My 3 y.o daughter is always complaining about having stomach aches after she eats. what can be wrong ?

Gastrocolic Reflex: Occurs when a stretch on the stomach increases the motility of the colon. Having a " full" stomach creates an urge to have a bowel movement. Your daughter may sense this as pain ; complain in the middle of a meal because her stomach is smaller than an adult's. If there are no other symptoms, allow her to go to the bathroom, wash her hands ; come back to the table till excused.