I had blood mixed inside my stool 1 time then went back to normal.the night before i was constipated and strained .recent colonoscopy.diverticulosis?

Bleeding: Most likely hemorrhoids. Diverticular bleeding is painless and rather large in volume. It would scare you if you never saw it before. Glad to know you had a colonoscopy to work it up.

Rectal bleed?: if the blood you noted were bright red, then the bleeding would likely be from a hemorrhoid or an anal fissure, either of which can result from straining to pass a difficult stool. If the blood were more black and created an entirely black movement, the blood would be coming from an upper tract source such as an ulcer. Bleeding from diverticuli is rather dramatic and scary.