C.M.
My daughter had the same problem. She would have sever stomach pain that ended in ER trips. I took her to an allergist when she was 4 years old. Negative on ALL testing and blood test for celiac came back negative. She is now 8 years old. She was STILL having problems. When she was 7 (almost 8) I took her to another allergist. She had a long list of positive skin test allergies. Dr put her on an elimination diet. It took 2-3 months to get through the whole list. Everything that we tested back into her diet was fine, EXCEPT for wheat! She does not have celiac, but an actual allergy to wheat! She was also having an actual allergic reaction though with severe hives all over her body with it. Last week we were at an amusement park and they said their fries were gluten free. The next day she was in SO Much pain. No, they were not gluten free :(
I think the best way to find an allergy is doing an elimination diet. I hope she feels better and you find out what is causing her pain. It took us almost 4 years, but ever since we found out, things have been much better