It is understandable that you should feel rejected by your boyfriend's lack of interest in having sex. However, the fact that your boyfriend is having blood in his stool for 5 years is a very serious concern that needs immediate medical attention. I don't care if he doesn't want to see a doctor, it is imperative that he does.
If you re-read what you wrote, I think you will find clues to why your boyfriend is not interested in having sex. It sounds like he does hard, physical labor, is concerned about paying his bills. is not taking care of his health. It is possible that he does suffer from erectile dysfunction. I suggest, that instead of arguing about not having sex, you urge him to get a complete physical examination with his doctor. If he cannot afford a doctor's visit, consider a health clinic. Hospitals and community centers often have clinics with a sliding scale payment based on a person's income.