Why does my penis smell even after a shower and washing and scrubbing througholy it still smells?

Need to be examined. I would suggest you to consult with either an urologist or dermatologist. What is the odor like? Is there any rash? Is it contamination from another person through sex? Are you putting creams or lubricants, perfumes to shave genitals? Is it allergy to the underwear? Rule out infection.
Hmmm??? Hard to give you a definitive answer without examining you and reviewing your health history; my advice is to get to your primary care doc and discuss this with him/her. Best of luck.