this can be due to many things but certainly needs to be checked out. things that can cause blood from the rectum are hemmorrhoids, polyps, fissures (little cuts), and even cancer. to rule out the more serious you need to see your dr for an exam and proceed from there. if the bleeding is light and no pain and doesnt get worse you can probably wait until monday but to be totally safe you should try to see someone today and get treatment if necessary.