Hiya I Need Some Help And Advice. My Penis Size

Hiya I need some help and advice. My penis size is worrying me badly and I am being very paitent. When I turned 14-15 when I hit puberty my pubic hair started to grow, voice deeper etc. But now at the age of 20 my penis hasn't grown because I don't know whether it's to do with masturbating or I should stop doing that which I have done to see what happens after. So I don't really know what to do :(