My rheumy tested me for celiac disease and I don't have it. But after struggling for years with inconsistent bowel movements, some bowel pain that might or might not be inflammatory and a lot of tests to eliminate the obvious, my GI finally suggested I just try a GF diet. It worked wonders.
What the GF diet did for me: whatever joint pain I had even with the sulfazine disappeared. My loose stool got solid. My ability to concentrate improved (although I wasn't aware that it had gotten bad!).
I still struggled with inconsistent motility, and I've been using psyllium capsules to help improve that part of my life.
It is possible to have an intolerance to gluten and not have celiac disease. It may be that your chronic inflammation has affected your ability to digest gluten. It is quite well known by now that people with Crohn's have a disordered gut microbiome, and it is also well known that digesting gluten requires a certain population of gut bacteria in addition to enzymes your body provides - it is not surprising to me to figure out that I cannot tolerate gluten.