There's a simple blood test that can be done. If that comes back negative (as it only tests to see if you have an active form of the disease) you can opt for genetic testing which is something like 10 tubes of blood? It's a lot, due to other issues I have, I am usually a bit anemic so when the lab managed to contaminate the lot of blood I gave, I had to wait a few weeks before the Dr okayed them re-taking the blood.
If you have the either of the faulty genes you technically *have* Celiac Disease but in an in-active state, you are fine eating gluten.
As another Chronic Illness I have (Ulcerative Colitis) has the same symptoms and I have a yearly colonoscopy, my Dr chooses to do an Upper Endoscopy at the same time to check for damage which would be done by Celiac Disease. Because I already have somewhat precarious health, it is vitally important that an active form of the Celiac Diseas be caught very quickly, which is the reason for the upper endoscopy. Other family members who do not have UC just have the blood test done. The only caveat is that you must be eating Gluten up until the test or the blood test will give off false results.