on the underside of my penis, there is a darker colored band that runs from the base to the tip of my penis, anlong the same line as my urethra. I realize that some guys have this and some dont, and that with some people its lighter and darker than others. however, i believe that from masturbation, and the way that my hand is positioned and pull on the skin on my penis, that closer to the tip of my penis the straightness of this darker line is a little curved. anyone else have this problem? maybe its just been like that all along, and i just realized it now. I have seen it before, but im just wondering if its at all common. thanks for any input.