I second Sascot & David's suggestion on testing for fecal calprotectin as well as celiac, food allergies, and parasites. Be sure to get copies of all the lab work so you can do your own research as well.
Whatever you do, don't give up. If you're not getting answers, get a second opinion. Our first GI doc kept ignoring the inflammatory markers and said our son was fine. Well, on the OUTSIDE he was fine. Inside he was a mess with a 6" stricture! Keep pushing, keep asking questions... and keep us posted.