i don't think u should force yourself to be sexy like that. when i was in my teens, i made it my mission to figure out how to look and feel sexy without being revealing. honestly, if ur just showing off ur assets without actually revealing skin, it can work really well too.
for example, if u have nice boobs, u can wear a tight top rather than a plunging one. or if u have a nice butt/legs, wear a fitted knee length skirt, instead of a shortttt skater skirt.
stuff like that. of course from time to time u can amp it up a little but i mean when u know how to style yourself according to your body, u find out that sexiness is not in how much skin u reveal, but in the way you own the clothing.
You dont need revealing clothes to look sexy. I would try a little something different just to try and put yourself out there. But you can always just style up and wear clothes that aren't revealing but are good fashion. Just go and shop around with friends or you can do it by yourself and ask the assistant to help. They usually know what items are hot since they sell it all the time and if the assistant is good she will know what clothes will work for you.