I understand they have a test for Celiac if you want to know for sure. However, I thought I heard that it only works if you've been eating gluten for a while. If you've been pointedly avoiding it as I have, it may not work. I'm not sure about that though. Ask your doctor.
EDIT: Gluten-intolerance is a slower, less obvious reaction and maybe very different reaction altogether and I'm pretty sure they don't have a test for that. It's still controversial whether it's even a thing. The theory is that if you aren't able to digest the very long protein strands thoroughly enough, the remaining bits act like tiny microscopic shards of glass in your system. They can (theoretically) tear through the lining of your intestine and get into your bloodstream and make microscopic tears in cell walls anywhere your blood carries them (your whole body), thereby causing sort of random, general inflammation. If the holes in your intestine get big and/or numerous enough, you can (theoretically) start to get bits of poop in your blood and thereby even more inflammation. It can even (theoretically) lead to hormonal problems if they, for instance, cause inflammation of your thyroid or pituitary gland, which could then interfere with their normal function. I read an extensive paper on it once. It was pretty interesting.
I used to be very confident I was gluten-intolerant as I just described. Now that I know I'm prediabetic, all the symptoms above can also be explained by high blood glucose levels which glutenous foods are likely to induce. So basically I'm no longer confident I have a gluten-intolerance. I seem to be able to eat very small amounts and not feel anything negative.