Yep, I was in almost exactly that situation and the doctor said something along the lines of "it's almost always a hemorrhoid, but we'd better schedule you for a colonoscopy just to make sure" and sure enough there was a tumor that wasn't cancerous yet, but could very well have become so and killed me in a few years if nothing had been done.
(It runs in the family apparently; my grandmother on my mom's side was from a large family, with seven or eight siblings. They all died of colon cancer. She got it too, but since she went to the doctor with her symptoms instead of staying at home, they were able to remove part of her colon before it got really bad and she lived for many more years.)
Moral of the story: go to the doctor if you're bleeding from unexpected places.