I suggest you have a look at this thread:
http://forum.nihonomaru.com/ask-girl/20212-size-small-you.html
But i guess it must be hard on you not being able to live up to the expectation of black men having a 25cm (10inch) penis. I wonder who's to blame for this ... I'm looking at you, porn industry and media!
But rest assured, 15cm is actually a bit larger than the international average penis size. You have nothing to be ashamed of.