question... please help?

Im16 and im pretty mature in body ize im 6'1 and 285 lbs, but since the first time i ever got an till now my has never grown, its about 5 inches (ive never really measured it, just a estimate) i can , but i am conserned, my is only 2maybe 1 inch when flacid. then when i get an it grows, so from a flacid standpoint my has never grown.