I'm younger (19, 20 in a couple of months) and i've been on a few "dates" but no girlfriends so far. i say "dates" because i've been on one date where i asked the girl out, and a few others where i think the girl viewed it as a date but i did not.
the one date i asked her out on didn't go well. i wasn't interested in her, i found her quite dull. i tried to make interesting conversation but she had nothing to say that interested me.
the other time it was with a girl i was really good friends with (still am) and i had a crush on her, she was also pretty interested in me. this was when i had really low self esteem. we hung out and looking back i can see that she was interested in me but i couldn't see it at the time so i think i ruined my opportunity before i knew i had one.
anyways, my problem isn't so much that i don't have the confidence to ask them out, i'm just not interested in enough girls to ask them out.
i have a question for you. do you go anywhere where you could meet girls (school, bars, stores, anything)? if not, that's your first problem. start spending some time at places where you can actually meet people and talk to them. if you are going to those places, then just start taking small steps to build up your confidence. first just start talking to people, don't worry about dates or anything, just try to start a conversation and try to keep a conversation going. this will get easier and easier with practice. once you're comfortable starting a conversation, after a good conversation, ask the girl for her number. some girls won't give it to you, that's fine, most people get more rejections than numbers. if you get the number, then you know she's at least a bit interested in you so you can ask her out on a date sometime.
when you start talking to people, don't worry about getting something out of it, just try to learn how to talk to people. see what works and what doesn't, remember that and apply it to the next conversations. eventually it'll start to become more natural and you'll be able to hold a conversation without even thinking about it (that's what i'm hoping for anyways). I can usually make ok small talk, and i can usually make some sort of small conversation with someone depending on the situation. you might never become the king of the party but you'll probably at least be able to fake interest in someone enough to socialize normally.