Not to be to graphic, but if you have blood in your stool (especially if it is dark red in colour rather than bright red), then you should take yourself immediately to the doctors and tell them. They can take a stool sample and if necessary, refer you for a colonoscopy.
You can be sedated for the colonscopy if you don't like the idea of being awake for it under a local. You normally get a dose of Propofol injected into you (like Michael Jackson) and you wake up feeling refreshed and slightly pissed off that the nurse dared to wake you up from your beautiful embracing slumber. The procedure really isn't as bad as you think it is going to be. The preparation for it is much worse (not painful, just unpleasant).
You will then know for certain whether or not you have a really nasty cancer problem, or just plain old piles. People with Ulcerative Collitis and Crohn's have a higher risk of bowel cancer, so it important that they get checked regularly (talk to your doctor).
Don't delay. It could cost you your life. Men are often the worst for procrastinating over such a decision.
Update - I don't want anyone to think that I'm am suggesting Alex delayed seeing a doctor btw. I just wanted to impart some general wisdom that might save someone else's life.