black veins and bruising on penis ?

I seem to have this black stripe down the center of my shaft, it goes about half way up and also goes into the scrotum where there are some, what looks to be swollen, more dark coloured veins. These veins in the scrotum aren't black but they are darker than the rest. I also have a lot of discomfort in the head of my penis, It's like a burning feeling, sometimes like i gotta itch it. When I take a pee I noticed that after-wards, about a minute, it feels like a bunch of pee or sperm move up into the head and stay there, making me feel like i gotta pee again. What is happening?