How to be more confident?

Well as a guy I can tell that its because you dont let the guys go for you. Once they start going for you, you may be the kind of person to shy away and when guys sense that they know to back off. If you would open up and let them advance more guys sould go for you. P.s.: try to act intersted but hold on until they get to know you better. If they ask you out, just tell them you want to know them better.