Hi, Something That Has Been A Lot In My Mind

Hi, something that has been a lot in my mind lately is about the size of my penis. I am a solid 3 inch flacid and a solid 5 inch erect. Is this normal for a 17 year old? I've heard that it may grow up a little more but i have masturbated a lot, does masturbation stops the growth of the penis?
I am really subconscious about my penis size...