I have diarrhea after I eat dinner a couple times a week. What could this be? Stress?  I had a colonscopy a few years ago, everything was normal.

Malabsorption? Chronic diarrhea related to food sounds more like a malabsorption. Have you checked for celiac disease, lactulose intolerance, or allergy to certain food? Intestinal bypass surgery can have similar symptoms. Stress certainly will cause diarrhea such as in IBD, usually not food-related. Stool characteristics may give you clue. Normal colonoscopy makes inflammation or other changes less likely.