Sorry to hear that you're going through so much but the fact that you're doing so much research is great and you will always be your own best advocate. Your symptoms could be from many things and celiac could definitely be one of them. Your endoscope will provide you more information (I missed whether they did a blood test for you for celiac?) and perhaps they'll do a colonoscopy as well?
If all turns out normal you may want to try a gluten free diet anyway and there are other diets that may help you as well like the low FODMAP diet. Some people are sensitive to many different foods other than gluten like dairy, corn, soy, excess fructose etc. so a lot of symptoms can be alleviated by diet as long as your other tests don't show anything else like IBD.
Hang in there and wait for your test results and definitely consider diet, vitamin supplementation and perhaps a gentle laxative to keep things moving - Miralax has limited side-effects but you should speak to a Dr. as I'm not sure how it would interact with anything else. My dietician recommended Spa Tone as an iron supplement which doesn't cause crazy constipation like most other iron supplements. You can also try eating things like cooked spinach, clams and then taking vitamin C to increase the absorption of iron.
Let us know how everything goes - there are a lot of people on here who can offer amazing advice.
Many of us have residual effects after going gluten-free. While it is sometimes an instant cure lots of people have to investigate further medical conditions, dietary sensitivities and vitamin deficiencies. From what I've heard and experienced, fructose malabsorption can cause the same type of brain fog and while I can't supply you with the link there's definitely a medical study done on this. Other things to look into are vitamin deficiencies like B12 and Iron and as others have mentioned thyroid issues. You can also look into the low FODMAP diet which lets you know what fruits are excessively high in fructose. The good news is that you've made some progress and that you've seen improvement. Just hang in there and take it one day at a time!
Sounds a lot like appendix issues - I thought I had some before and when I was reading through your description it sounded like it. Where are you located in Canada? Usually they triage people according to their needs. If you say you're in 100% pain, can't sleep and think it's your appendix then they might prioritize you. Alternatively, you can wait until 4:00am or 5:00am or so and go when no patients are around. I personally wouldn't wait - I wouldn't necessarily associate specific pain with celiac - your pain is where the small intestine meets the large intestine and where the appendix is located. I wouldn't mention celiac if I went back to the ER as they might not be open-minded about other causes. Just my opinion! Hope you're feeling better soon.
I have secondary adrenal insufficiency and diabetes insipidus. Good on you for even knowing what adrenal insufficiency is! I was sent to the Endocrinologist for blood sugar problems (due to low cortisol) and he figured things out from there.
I'd meet with the Endo again to get properly tested. I'm on replacement cortisol and has it ever made a difference - I would have been in serious trouble without it a few times when I got sick so I'm happy to have figured this out. I have to say I haven't been glutened because I'm on a very limited diet at the moment and don't eat out but you should get tested for hormone levels and then get tested for vitamins and overall health (B12 and Iron especially). If you're in an accident or a similar stressful situation and your body can't produce cortisol then it can be very serious so it's best to know.
Too bad the hospital messed up...can you see an Endo and have him supervise it? I went to a specific clinic and he stopped in a few times to make sure it went well.