Your biggest problem is that you're desperately searching for one. I don't mean that harsh. I'm hoping this will help you realize a few things about yourself. Everything I tell you is from personal experience.
You think you NEED a girlfriend. The truth is, you WANT one very, very badly. That shows that you are unhappy with yourself in some way. You don't feel satisfied with who you are because you think no girl wants you. Your lack of confidence is actually what keeps you from getting a girlfriend.
That said, there is no "how to find a girlfriend". If it is supposed to happen, it will happen by chance. If you try to force a relationship, it will not end well, guaranteed. Don't confuse chance with the "let her come to you" routine. When I say chance, I mean you will meet a girl, you'll become friends, while friends you will start developing feelings toward each other, you might try dating for a little while, your friendship will turn into a relationship, your relationship will turn into love, and result in engagement, marriage, and children. Assuming everything goes as you hoped (and didn't force), this is what will happen.
I hope this helps you regain some confidence and self-dignity. Take pride in who you are (but not too much, remember God said we are to be humble, assuming you believe in God of course). The main thing is to be happy with yourself. If you're not happy with yourself, it is impossible to be happy with someone else.