A fissure is a tear in the rectum. They tend to hurt a LOT. If you're not having severe rectal pain, then hopefully, you just have hemmies (internal or external). I have internal and external hemmies and have had many fissures. I think most of my bright red bleeding has come from the hemmies. It can look like a lot more blood than it actually is....but you should get a checkup to make sure what's going on and have your hemoglobin checked for anemia.
Good luck to you!