Hi Im sorry to hear you are suffering like this. Why don't you go to the Accident and emergency part of your local hospital and get assessed? Causes could include a stomach ulcer,ulcerative colitis,bowel cancer or haemoroids. There must be something going on in your digestive system. It doesn't mean its serious but you need to let the doctors have a look soon. Don't worry as mostly there is good treatment. Look after yourself,all the best.
Rectal bleeding is never normal and you should seek medical advice. For further background information, google rectal bleeding and click on to one of the many sites - the Medicinenet site is particularly informative.
regards
Morecambe