Cancers are typically diagnosed for older age people, but not necessarily. The precise reason for the cause of colon cancer has not yet been identified but it is believed that genetic predisposition and carcinogenic substances from food are possible causes. Only a colonoscopy can confirm or exclude colon cancer. Cystoscopies can confirm or exclude bladder cancer. Chronic prostatitis can cause some of the problems you describe (pain and urinary retention) and can be investigated further with help from a medical professional.