How do I become confident?

I basically don't have any confidence at all. But I don't walk around all depressed about myself either. I don't think I'm attractive, but I don't care. But the problem starts whenever I start liking a girl. For some reason I'm really picky about girls. They are always really pretty and I have no problems talking to them, I just never think I'm anywhere near good enough to get with a girl like that I so I don't even try. I don't think there is something really wrong with the way I look. I know I'm not the worst looking guy out there but I'm definitely not the best. I'm just your average guy. 17 years old, 5 foot 11 inches, 142 pounds, Hispanic, slightly tan but still light skinned, slightly long black hair (more on the short side but still has some length to it), greenish hazel eyes, decent skin, braces wouldnt kill me but :/. I dress like a normal teenager. Skate brand shirts ( I do skate), skinny jeans ( not too skinny or too loose, just fit) I don't sag, and match well. But im never able to talk myself into asking the girl out on a date. Im always convinced that I'm no good for her. I just can't change the way I think of myself. I've always been like this. and when I talk to other people about it and they tell me stuff to try and boost my confidence I just think they're trying to be nice. I never take compliments from my family seriously, it's like bragging about your mom saying you cool. And yes I know I went on a bit of a rant but it's hard to explain it when I'm not saying it person. And I'm not going to walk up to strangers and ask soooo yea.