Some studies, with admittedly small sample sizes, show that about 50% of celiacs react to the protein casein in dairy the same way they do gluten. Can't find the NIH article I'm looking for but this one basically makes the point:   

I was diagnosed in April. I have been very careful about being gluten-free, except for one accident in August where I ate candy with wheat. Despite being careful, I still experience extreme painful bloating almost daily. I'm so frustrated. I stopped eating gluten-free oats because I wondered if that was it. Now I am wondering if is dairy. I'm already tired of constantly wondering if I messed up.

In general I'm all for a formal diagnosis, except in cases where someone gets very sick when they eat gluten, and have already been on a gluten-free diet for a long time and don't plan to eat it again anyway. There seems to be more drawbacks that keep popping up with being formally diagnosed--at least here in the USA. I can testify that it's definitely harder to obtain life insurance, and if you can get it the premiums are quite a bit higher than if I did not have it, at least from my fairly recent experience when getting a new policy.  @Ginger38 you're very close to the end of your challenge, so let us know how it turns out.

Just to add something here... if any people in the UK are reading this, there can be definite advantages if you are formally diagnosed coeliac,  in terms of getting extra support from the NHS.  For free you get to see a nutritionist, additional vaccinations if deemed necessary, in some areas prescriptions for gluten free food; bone density scans, annual blood tests and reviews with a gastroenterologist, plus it has been my experience I've been able to see a gastroenterologist without a GP's re-referral when I've had complications.  That said, I don't know what impact there would be on health insurance; but I have found that when it comes to travel insurance I have had to declare it but it hasn't made any difference to the premium. However, I realise things can be very different in other parts of the world, and I am not sure where you are from, @Ginger38  

Yes I figured out I couldn’t have gluten years ago when I was symptomatic and tested positive, but was misinformed and told I couldn’t have celiac but to go gluten free. I was already gluten free. I was never willing to go back on gluten and make myself so sick to have the biopsy especially when the biopsy isn’t 💯. But Now I have to have a procedure anyway and he told me he was doing the biopsy either way .. but I should consider the gluten challenge since I have never had the biopsy. He acted like it was super important to have this on paper.  I had no idea there were any possible negative drawbacks to having a formal diagnosis 🤦🏼‍♀️