What Causes Bowel Movements After Eating?

My daughter is three and a half years old, she weighs 16kgs and is very lean. For the past couple of days she had been passing stool soon after her meals. She passes stool 4-5 times a day, although it doesn t appear anything like diarrhea but her stool is a bit loose. Her appetite is fine, she is pretty much active but somehow her immunity is low, she falls ill frequently, most of the time its cough and cold. we did consult a pediatrician but the medicine seems to have no effect on her, the doctor mentioned that its due to indigestion but I wonder if its got to do with worms or some sort of infection. Kindly help me out Thanks in advance. Sreedevi.