seriously serenity, don't get too into making commitments at this age, especially seeing as they're life changing for her. just have fun. until you get to 25+ screw commitment and shizzle, just party, meet cool girls and have plenty of good times, if you catch my drift.
then again, if you stick with the same girl, you'll never know what you're missing. treat your girl more as a **** buddy more than your future wife
oh, and seriously, forget the marital sex bit