there are many causes for chronic diarrhea and crampy abdomens yes one of them is irritable bowels but infections inflammatory bowels ( esp crohns which affects the small bowels) food allergies and sentivity infections hormonal issues and stress factors some medications also well colonoscopy wont jus be an ideal thing. you might have to undergo few autoimmune disorder investigations, infections and allergies to be ruled out. even your intestinal flora changes due to allergies and infection be a major cause of diarrhea, lately due to no protocols in india, many such cases are treated as irritable bowels but then the cause is something else like chronic bovine tuberculosis also even eosinophilic colitis thanks dr tapan