I think that’s rather normal at 15 (for male or female).  I too was obsessed with the idea of having sex as well.  I masturbated quite often at a young age & by 15 pretty much everyday 2-3 times a day.  If you feel this is a problem for you and that it hinders your every day life then maybe you should try to refrain from doing it, find something else to do instead.  This is a hard one for me to answer, like I said I was very similar but admittedly it did NOT hinder my everyday life.  Any one have any advice to give?