Hi ! Possibly you had a constipated bowel movement which has cut through the anal area creating a fissure which has bled. With fissure usually there is pain involved, but you have not mentioned anything about the pain. If you are chronically constipated, then you may be having hemorrhoids, which has bled like the way you have described. There are a few other pathology which might give rise to such bleeding from your poop, but it can not be diagnosed simply with history or over the net. I would suggest you to get yourself examined by a general surgeon/gastroenterologist who may do a per rectal examination followed by an endoscopic examination if need be for diagnosis and further management. Good luck.