90mph, I'm exactly like you. Or, I was.. or is, I don't know! Me going out and sleeping with every man who wanted to was because I was trying to fill a void that my dad left me with. I know, such a cliche. Daddy didn't love me and now I'm a skank.
But yeah, do some soul searching and you WILL find a reason behind it. I'm bipolar so it's classic bipolar behavior, but there was still a subconscious reason for it.

I haven't had sex in 2-3 years, not since I broke up with my ex-fiance, and yes - I turn down men ALL the time. Sucks to be them!
Thing is, once enough time has passed - you forget how good sex feels, and you won't really care about it anymore. The last time I had sex (hadn't had sex with my ex for two months) I was all "OH MY! How come I don't do this more often??".

I think it's for the better that you try to end this behavior, or at least keep it at a minimum. You might be harming yourself, and you won't feel the consequences until later... like I sadly experienced. Plus, I ASSUME that you're more or less carefree about protection and safety and things like that; which can lead you into a heap of problems... like I sadly experienced. x)