Women don't just look at a guy's looks...really. They are very attracted to confident men, so why don't you stop being so hard on yourself, and look at the great qualities you do have to offer.
AFter she goes on a few dates with you, she might find she's really attracted to you, and not just for your looks alone. Actually, I read in one of Dr. Gray's books (the one who wrote Venus and Mars), that women actually become more physically attracted to a man when they are attracted to a man on the emotional level.
So, get your confidence up where it should be and take a chance. Like the other poster said, you will always regret it if you don't. The worse possible scenario is that she may say "no". Yes, your ego may get a little bruised, but so what. Just refuse to take it personally. Good luck.