Thanks for reporting back @Nicbent35! You seem to understand the options and the risks. So, it is a decision you will just have to make. But you don't have to make it right away. You might consider keeping her gluten-free for a while yet. I would give it six months before considering adding gluten back in. Make sure the improvement you are seeing is due to removing gluten and not something else that will pass such that you see a reversion to former behavior and symptoms.

If you have been on a strict gluten-free diet for several years, it would be normal for testing to show no evidence of celiac disease. No gluten, no inflammation. No inflammation, no antibodies and healing of the small bowel lining would result.  Personally, I think the doc gave you bad advice and I feel confident that trialing a return to gluten consumption would not be the advice that the vast majority of GI docs would give you. If I were you, I would seek a second opinion before resuming gluten consumption. 

So my daughter is almost 4, i posted in here before about taking her off gluten myself as an experiment due to behavioral issues she was having (very angry and extreme tantrums). I started gluten-free Feb 8th, I’m happy to report it’s like I have a different kid. She has an occasional tantrum now but the kind that I expect out of a 3 year old.   At the same time I also started giving her a magnesium supplement, probiotics regularly, and a supplement to help with her constipation. I also changed some methods with how I was dealing with her tantrums…problem now is I’m wondering should I try to put her back on gluten and see how she does?? I never consulted with a doctor, never got her tested..I just did this on my own. But I have to admit I’m scared to screw up the progress we have made and scared to return to that old behavior. But at the same time, I don’t want her to have to live gluten free if it’s not necessary. Any words of wisdom with those more experienced with this? Someone suggested I try her on non-gmo gluten because she may not react to that?   Let me make clear tho, I’m very willing to continue to keep her off gluten if that’s what’s best but it’s hard to know at this point. 

Yes, in 2017 I had all of the blood tests and several endoscopies.  All of these indicated Celiac Disease.  I have had endoscopies every few years since, and my last one was a year ago.  This is a new GI doctor for me.  The results he put into my medical record said, "No evidence of Celiac Disease".  Today, he recommended that I start eating gluten again to see if I get sick from it.  I did not misinterpret him or my family practitioner.  I asked several times if his diagnosis actually meant that my Celiac Disease is well controlled.  He said no.   I'm absolutely gob-smacked.  

Welcome to the forum, @jkinloch! That is unusual because celiac disease is a genetically based autoimmune disorder. One the latent genes are triggered such as to produce active celiac disease they are "on" permanently. Celiac disease doesn't go away.  But first, let's establish some fact-based history before we speculate any further about how this change of tune by the GI doc came about. So, first of all, how did this GI doc arrive at his original dx through normal celiac testing protocols. Typically, this involves two stages of testing. The first is a blood test looking for antibodies that are specific for celiac disease. The second is an endoscopy with biopsy looking for damage to the lining of the small bowel that celiac disease causes. Were either  or both of these done years ago. If so, what were the results? Were these tests repeated when he/she recently declared you to not have celiac disease? Are you sure you did not misinterpret what the doc said to mean you no longer had celiac disease when what he really meant was that your celiac blood antibodies had now returned to normal and the lining of hour small bowel had now healed. That would not be the same as "not having celiac disease".