Why won't I ask a girl out?

I'm going to be 20 years old soon and I can't seem to bring myself to ask out a girl. I'm very charming and decent looking and some pretty attractive girls have liked me (some even currently) but I'm always sabotaging myself. Also even if I don't, I feel like because I drive a really beat up car and don't really have income, have a poor family life, and am not where I want to be personally or professionally that it's not the right time to ask a girl out. But I don't know why a girlfriend can't be mutually exclusive in my mind. Also, I vary on my self-esteem levels. My father is overbearing and casts a large shadow so I think I worry about measuring up to him (he was a big time womanizer); also I was hurt bad the last time I pursued a girl and I think in all things I've built a wall to stop me from letting any emotion get in - I hardly cried when my grandmother died, only several months after - in private. I think I'm afraid to let anyone get anywhere close to me. My friends keep teasing me that I don't want to have sex because the amount of attractive women I've had opportunities with that I've screwed up or pushed away. I'm worried I'll never have a relationship. Advice?