Sharon, If memory serves me right you are the one who started that thread titled
Preserving a Platonic Friendship in March. Maybe the reason why that guy friend of yours never tried to have a romantic relationship with you is because he saw that you had the potential to have a "wild adventure" as you described in the first post of this thread, and he didn't want to get involved with someone who'd engage in such risky activity.
Maybe the reason why this male friend of yours---whom you described as a good catch but whom you really didn't seem to have any genuine attraction---didn't date you is because he did see that you have very low self-esteem in yourself and knew that you might have gone on such a "wild adventure" behind his back if at any one point you were feeling down and couldn't find comfort in him.
I think you should talk to a professional because I fear your feelings of low self-worth might drive you to do something more rash and potentially fatal in the future. Also, I'm curious as to the kind of guys you go for and whether that has anything to do with your feeling unpretty and undesirable. Somehow I have the feeling that you go for guys who treat you badly because they're a challenge and you think the "nice guys" like that male friend of yours that I mentioned earlier are too weak and boring for you. Maybe it's time you change your circle of friends and start hanging around people who treat you right and respect you... maybe you'll learn to appreciate and respect yourself more.