I have blood in stool. i've had 4 colonoscopy. negative results. had diverticulitis before. what could my problem be?

Maybe not colonic...: Evaluation is always appropriate for re-bleeding from the gut. Black stool often means bleeding from upper GI tract; grape jelly stool from small bowel; silver stool from biliary tree; burgundy stool from right colon; red blood from left colon to anal canal. Any accompanying symptoms? Do you take NSAID's, over-use alcohol, smoke tobacco, have other risks (AVM's for example)--lots to consider.