I have bright red blood on the tp when I wipe my bottom... it only happens when I have a bowel movement and was wondering what could cause it and what it could be?

UPDATE: this recently just started happening. My stool isn't any different than it used to be. It is still normal. I've had harder stool and I've never bled before. There's no pain and each time I wipe there's more and more blood. It starts out as a little then it's a little more each time I wipe.