hi cupcakes (&CMOT :))
similar story here, went gf when my ds had to, although we declined biopsy for him too, the change for the better has been amazing (it's now been 5 years+).
What I noticed on my ds though was that after first mega improvement, he developed some strange symptoms, like prolonged fungal infections, ticks, echolalia, I was quite worried.
I carried on researching what any of this could be linked to and discovered that he continued to be still deficient in some vits/minerals, esp zinc, magnesium and B vits (and he was vegeterian), this came out of the hair testing, but I think blood tests are available too.
You could maybe ask your dr for some blood tests to check if you are now absorbing everything OK, esp fat soluble vits A,D,E,K, also Zn, Bs, Mg, Se etc. Even tho my ds consultant was confident that he should be OK in terms of correcting deficiencies after 6 months or so on the diet w/o supplements, tests after 2 years showed he wasn't. I then started gently supplementing a few things and bingo, after a noticeable plateau, he continues to improve, to the point that teachers have noticed.
It also turned out that he was too high in copper (toxic) and too low in Zn, by supplementing Zn, copper gets pushed out. Also, Zn is very involved in immunity and enzymes production, all good things, and frequently deficient in gluten-related problems b/c it normally gets absorbed quite high in the gut - where gluten gets in the way most.
If you don't want needles, try a hair test (it was private), but best to wait for about a year after the start of the diet so then you test the post-diet hair.
I never bothered testing myself, I just take occasional supplement alongside my ds.