It is perfectly normal to be that big at your age. Hell, there are some men who are 30 and only 5 inches long, if not smaller so feel lucky, you got a decent sized penis. I heard from a friends mom that men with long penises think they're all that and they suck in the sack, so, a 6 inch is fine, it means you might be pretty good in the sack eventually if you aren't already.