As you have posted your question on the colon cancer forum, I suppose that you fear that this may be the cause. It is highly unlikely because colon cancer is very rare under the age of ~40. I suggest that you type in rectal bleeding to google and click on to one of the many sites - the Medicinenet site is particularly informative.
From the description of your condition it sounds as if the cause might be one of the minor conditions such as anal fissure, haemorrhoids etc etc.
BUT - rectal bleeding is never normal and so please seek medical advice. With the added knowledge that I hope you will seek by googling rectal bleeding, you should be in a better position to have a meaningful discussion with your doctor. If your doctor is vague about the diagnosis (such as "well, it looks as if it might be .......") then you might wish to ask for a colonoscopy.
Thank you for you advise. I'm actually going to the doctor today.