My 10 Year Old Daughter Has Pain In Her Navel

My 10 year old daughter has pain in her navel area from time to time. She says it hurts and she feels like she has to go to the bathroom, but usually doesn't. the pain lasts awhile, then subsides. It even wakes her up in the middle of the night at times. We have tried, thinking it might be constipation, mirilax, but it is Not just constipation. I'm almost of the opinion it may be some sort of food allergy. Thoughts?