How come i have blood in my poop?

Varies: If the blood is bright red, it often relates to hemorrhoid problems. Sometimes heaving straining when attempting to have a bowel movement can rupture small vessel in the area. If stool is very dark (black), it may mean there is bleeding higher up in the bowel track (like an ulcer). Suggest you go to your physician and have examination of the area and a stool sample to determine.