Never act like anybody you aren't, ESPECIALLY slutty. You have your dignity, and most women I know who act slutty regret the day they started.
I'm betting that you carry yourself in a lady-like manner which is a BIG plus! Most guys our age aren't ready to handle that and get intimidated. But that's not your concern. If they're not ready, not your problem!
I know you feel a bit upset and you think your question sounds stupid, but it's not. I would say that it's normal to question yourself when other people don't respond the way you'd like them to do. So take advantage of this time! Figure yourself out; what do you want to do in life, and if a specific guy has a place in your life that you would be willing to share with him. Eventually, the right hot guy will come around.
If you're only getting approached by sleazy guys, it could mean you're sexy. Sometimes only sleazy guys will approach cuter girls because more normal guys are too shy. The creepers think, well I have nothing to lose, so I don't care if she rejects me, I might as well give it a try.
If you want to attract a certain type of guy, try to see what kind of girls they ARE talking to. See if you can make your style just a little more like that. Usually sleazy guys don't go as much for the more shy girls who are dressed more laid back.
My advice is to try out different looks and see what happens.