trents

Based on the available test information, it does not appear you have celiac disease. This is a assuming you are not IGA deficient and also assuming your gluten consumption was adequate both in amount and duration in order to ensure valid antibody testing. Guidelines for the "gluten challenge" have recently been revised. It is now recommended that those seeking testing should consume at least 10g of gluten daily for at least two weeks leading up to the day of the blood draw. 10g of gluten is about the amount in 4-6 slices of wheat bread.
Based on the information you have supplied, if you are convinced that gluten is causing symptoms, it would seem you likely have NCGS (Non Celiac Gluten Sensitivity) as opposed to celiac disease. NCGS shares many of the same symptoms of celiac disease but does not damage the lining of the small bowel as does celiac disease. There is no test for it. A diagnosis for NCGS depends on first ruling out celiac disease. It is 10x more common than celiac disease. Some experts feel it can be a precursor to the development of celiac disease. Eliminating gluten from your life is the antidote for NCGS just as it is for celiac disease.

I think you would do well to take a high potency B-complex such that you get more balanced dosage across the spectrum of B vitamins. They work in concert.

Welcome to the forum, @Kwinkle!
Realize first that the B vitamins are water soluble which means excess is excreted in our urine and does not build up in our tissues like fat soluble vitamins do. So, there is little risk of toxicity with large doses of the B's. 
Second, if you start with smaller doses they may not be large enough to be therapeutic and so will not help.
So, my recommendation is to start with high potency levels. But you also need to realize that the B vitamins work in concert with each other. So, it may not be a good idea to just to dose up on one or two of them. It might create imbalance. It would be a better idea IMO to take a high-potency B-complex. Make sure all supplements are gluten free.
If you live near a Costco, Nature Made Super B-Complex with C is a good choice.

I think you would do well to take a high potency B-complex such that you get more balanced dosage across the spectrum of B vitamins. They work in concert.

I don't see any point in seeking allergy testing to determine if you have a wheat allergy. I think you already know that you need to avoid use of skin care/hair care products that contain wheat and it's derivatives. 

Not long before my celiac dx I was experiencing proctalgia fugax but it seems to have disappeared and I haven't been bothered with it in over 20 years.

Yes, get serum antibody testing done for celiac disease. You could also have NCGS (Non Celiac Gluten Sensitivity). NCGS shares many of the same symptoms of celiac disease but does not damage the lining of the small bowel as does celiac disease. There is no test for it. A diagnosis for NCGS depends on first ruling out celiac disease. It is 10x more common than celiac disease. Some experts feel it can be a precursor to the development of celiac disease. Eliminating gluten from your life is the antidote for both.

Our insight into the immune responses involved in celiac disease has steadily increased and there have been many attempts to develop drug therapies to either break down gluten before it triggers immune system responses or to, in some way, trick the immune system into no longer identifying gluten as a threat. So far, all these attempts have been disappointments that did make it out of the trial phases that all new drug therapies are put through.

Welcome to the forum, @KCGirly!
From Wikipedia on Semaglutide: "The most common side effects include nausea, vomiting, diarrhea, abdominal pain, and constipation."
How much gluten are you consuming daily? Recently revised recommendations are for the daily ingestion of at least 10g of gluten (about the amount in 4-6 slices of wheat bread) for at least 2 weeks prior to celiac disease testing, either via blood antibody tests or endoscopy/biopsy in order to ensure valid test results. Your GI doc's instructions barely fit into that time window. I hope it is sufficient to yield valid biopsy results.
About your episode(s) after reintroducing gluten on 12/23 after starting a gluten free diet on 11/29. You stated at the outset of your narrative that historically these episodes occurred about every two weeks and that was before you trialed the gluten free diet. I would point out that you had only been eating gluten free for three weeks before the episode on 12/23. So, I'm not sure you can attribute that episode to the return to gluten consumption. 
In addition to celiac disease, there is another gluten-related health issue known as NCGS (Non Celiac Gluten Sensitivity). NCGS shares many of the same symptoms of celiac disease but does not damage the lining of the small bowel as does celiac disease. There is no test for it. A diagnosis for NCGS depends on first ruling out celiac disease. It is 10x more common than celiac disease. Some experts feel it can be a precursor to the development of celiac disease. Eliminating gluten from your life is the antidote for both.
Also, can you specify which test or tests for celiac disease were ordered by your GP? There are a number of serum antibody tests that can be run in order to detect celiac disease but many physicians will order the minimum instead of a more extensive panel. What one test misses, another may catch.

Well, I strongly disagree that it was a comprehensive celiac disease panel. In addition to the tTG-IGA and the Immunoglobulin A, a comprehensive celiac panel would have included DGP-IGA, DGP-IGG and TTG-IGG. What he ordered was the most popular celiac antibody test available (and perhaps the best one), the tTG-IGA and he also, to his credit, ordered the Immunoglobulin A (aka, "total IGA"). The total IGA test is not a celiac antibody test per se but is used to check for IGA deficiency. IGA deficiency can distort IGA test results for individual IGA test scores downward and create false negatives. You are not IGA deficient so that is not a problem in your case.
Here is an article giving an overview of celiac antibody testing: 
 

BadHobit, did you know that 40% of the general population has one or more of the genes that have been associated with the development of celiac disease? But only about 1% of the population actually develops celiac disease. So, the gene test can legitimately be used to rule out celiac disease but not to confirm it.

Even 10,000 IU daily should be safe for as long as it takes to get your levels up to snuff. Historically, early on concerns about toxicity concerns from D3 supplementation have proven to be to be overly cautious.

Let me "ditto" Cristiana's welcome to the forum, @DayaInTheSun! Many in this online family can identify with your struggle.
With all of your food sensitivity/intolerance issues you probably should research MCAS (Mast Cell Activation Syndrome) and consider a low histamine diet.

Early on,  DQ2 and DQ8 were the primary genes that have been connected to the potential to develop celiac genes but more recent genetic research suggests there may be more.

He could also have NCGS (Non Celiac Gluten Sensitivity) for which there is currently no diagnostic test per se. It is diagnosed by symptomatically reacting to gluten consumption similarly to those with celiac disease when the celiac tests are negative. In large part, the symptoms are the same, the long term health risks are the same and the antidote is the same - total avoidance of gluten.
By the way, RShisler. Welcome to the forum!
Do you have access to the blood antibody tests results and would you be willing to post them here? We would also need the reference ranges for what is negative and positive in order to make sense of them. Different labs use different reference ranges.
Unfortunately, there is still a lot of ignorance in the medical community with regard to gluten-related diseases. Many doctors neglect to tell their patients they need to be eating gluten before testing or they aren't aware of the need to. More than likely, you will find more good information about gluten related diseases on this forum than you will from the average physician.

Let me "ditto" Cristiana's welcome to the forum, @DayaInTheSun! Many in this online family can identify with your struggle.
With all of your food sensitivity/intolerance issues you probably should research MCAS (Mast Cell Activation Syndrome) and consider a low histamine diet.

Welcome to the forum, @Travel Celiac!
The high total IGA does not indicate that your celiac disease is actively flaring up. Total IGA is not a test for celiac disease per se but rather is test given to determine if you are IGA deficient, which you are not. IGA deficient people will experience artificially low individual IGA antibody tests such as the tTG-IGA and can result in false negatives. 
The other question is why is your total IGA count high? That can indicate other health issues besides celiac disease so I suggest you research that question and also talk to your physician about it. Here is an article that explains the various tests that can be run to detect celiac disease and the significance of the total IGA test:
Having said all that, I gather that for some reason you are under the mistaken impression that, having been diagnosed with celiac disease some years ago, your recent antibody test should still show elevated levels if you actually do have celiac disease, at least when you have accidental gluten exposure. I think you misunderstand how this all works and what the testing is designed to detect. 
When someone has celiac disease, the consumption of gluten triggers an autoimmune response that, typically, causes inflammation in the lining of the small bowel. This inflammation produces specific antibodies that can be detected by serum testing specifically designed to look for these antibodies. Upon the onset of celiac disease, it can take weeks or months of consistent exposure to gluten for the serum antibody levels to build up to the point where they are detectable by the tests. Once gluten is  removed from the diet, inflammation begins to subside and antibody levels begin to drop. An occasional gluten exposure will not result in restoring antibody levels to detectable amounts once they have receded to normal levels after going gluten free. Again, it takes weeks or months of consistent gluten ingestion for the antibody counts to reach sufficient levels to produce a positive test result.
Yes, you still have celiac disease but it looks like from your recent tTG-IGA test result that you are doing a good job with the gluten free lifestyle.

@gfreenc, there is no gluten in milk, whether human or bovine. Gluten is a protein in certain grains but it is broken down into various amino acids during digestion before it gets into the bloodstream and thus it will not wind up in milk. 

I think most of us, when we first got our diagnosis, imagined that going gluten free would be the magic the bullet that would restore us to perfect health. We soon find out that it usually isn't quite that simple and that celiac disease has long fingers.

BadHobit, did you know that 40% of the general population has one or more of the genes that have been associated with the development of celiac disease? But only about 1% of the population actually develops celiac disease. So, the gene test can legitimately be used to rule out celiac disease but not to confirm it.

Welcome to the forum, @Travel Celiac!
The high total IGA does not indicate that your celiac disease is actively flaring up. Total IGA is not a test for celiac disease per se but rather is test given to determine if you are IGA deficient, which you are not. IGA deficient people will experience artificially low individual IGA antibody tests such as the tTG-IGA and can result in false negatives. 
The other question is why is your total IGA count high? That can indicate other health issues besides celiac disease so I suggest you research that question and also talk to your physician about it. Here is an article that explains the various tests that can be run to detect celiac disease and the significance of the total IGA test:
Having said all that, I gather that for some reason you are under the mistaken impression that, having been diagnosed with celiac disease some years ago, your recent antibody test should still show elevated levels if you actually do have celiac disease, at least when you have accidental gluten exposure. I think you misunderstand how this all works and what the testing is designed to detect. 
When someone has celiac disease, the consumption of gluten triggers an autoimmune response that, typically, causes inflammation in the lining of the small bowel. This inflammation produces specific antibodies that can be detected by serum testing specifically designed to look for these antibodies. Upon the onset of celiac disease, it can take weeks or months of consistent exposure to gluten for the serum antibody levels to build up to the point where they are detectable by the tests. Once gluten is  removed from the diet, inflammation begins to subside and antibody levels begin to drop. An occasional gluten exposure will not result in restoring antibody levels to detectable amounts once they have receded to normal levels after going gluten free. Again, it takes weeks or months of consistent gluten ingestion for the antibody counts to reach sufficient levels to produce a positive test result.
Yes, you still have celiac disease but it looks like from your recent tTG-IGA test result that you are doing a good job with the gluten free lifestyle.

My best guess would be NCGS. Some experts in the field of gluten disorders believe NCGS can be a precursor to the development of celiac disease. Whether NCGS or celiac disease, the antidote is the same, total abstinence from gluten for life or at least until some scientific breakthrough occurs that allows those with gluten disorders to consume gluten. I think this is your next step, i.e., seriously committing to putting gluten in the rear view mirror of your life for good.

Duodenal ulcers are not uncommon either and often result from H.Pylori infections.
https://www.healthdirect.gov.au/duodenal-ulcer

I just want to reinforce what Scott said and that is we have tended to think in these neat little black and white categories of it's either celiac or NCGS when in reality it may not be quite that neat. There's just a lot we don't know and the immune system is very complex. I often wonder if I had been gluten free as a child if I would have avoided developing celiac disease as an adult. I think there is also this misconception that if you have NCGS, gluten is not harmful, it just creates discomfort and inconvenience.

Jula, welcome to the forum.
What possible benefit would having an official diagnosis give you at this point in your life? You already have medical test evidence that you are a celiac (antibody tests and genetic testing) and the symptom improvement when you went off gluten confirms what the testing already pointed to. Why on earth would you risk damaging your health by going back on gluten to get further confirmation of what you already have proved? You are now 15 years older than when you first went gluten free and your body will not tolerate the abuse it would back then. Call your GI doc and tell him you have decided to proceed as you are without the gluten challenge. If you want to go forward with the endoscopy to check for upper GI health in general, I can understand that but I certainly would not go back on gluten just to enhance the chance that you will receive additional confirmation of what you already know to be true. Are you having any other upper GI issues that you want to get scoped for?
Having said all that, it sounds like you may need to double down on your efforts to eat gluten free and now have the freedom to do that since you aren't any longer caring for your parents.