I'm scared of men and i dont know why?

I have this thing where it is verrry difficult for me to make friends with men because for some weird reason just the thought of being alone with them, or them wanting to hang out with me scares me. Im not neccessarily scared of getting D i dont think, just the thought of them being attracted to me freaks me out. Now its hard for even me to understand or pinpoint exactly, but when Im with a group of ppl and there are guys there I can talk to them, but then when it gets to be just one on one with us i get REALLY freaked out and antsy and just wanna cry or leave, or i'll feel depressed the rest of the day. But i have had plenty of boyfriends in my life, I am 18, just that there was something different about them that didnt scare me. I have only ever really had ONE close guy friend in my life, and that was because i felt a security that he was dating one of my best friends and wouldnt try anything, tho eventually there wwould be times where it felt like he was trying. Basically, not to be conceited, but I am a pretty girl, ppl tell me alll the time, i have low self esteem about it, but when i knoww that a guy is attracted to me, or i can FEEL them checking me out it makes me reeally freaked out and just depressed. I was ually molested once as a kid, and i am thinking maybe that might have something to do with my avoidance of strange men. I am not exactly sure, if someone knows anything about this area of stuff, or goes through it themselves or can help me, pleease help me, i dont wanna feel like this anymore :(