I am 27, been with and faithful to my wife for 4yrs. My last STD screening was 3yrs ago, all neg. Yesterday I notice a small red spot on the shaft of my penis. It is painless, there is no itch, & it is not raised excepts for a spot through the middle which is do to a tiny vessel running through it. Honestly It s hardly noticeable unless your in really good lighting. I have no other symptoms of anything, & feel quite well. Any thought on what it might be?