Don't worry too much about what you look like now. If the girls don't find you attractive yet, then so what. Instead of playing games on the computer, try going for walks, or riding your bike. Also try picking up an instrument.. if you haven't already. I know drums and guitars tend to be chick magnets. Tho personally I think dummers are better xD! To be honest... I can't stand hunky guys! Most of the time they are self centered jerks. Oh and to the people that won't hang around you, they don't know a good thing even if it hits them in the face with neon lights. Look for other friends to hang around.

You know what, being mature isn't so bad you know. I fall weak at the knees for boys who are mature. I'm 13 and have lots of 14 year old friends who are girls. Some of them are not into sex and hunk. There are lots of people interested in charismatic, intellecutual boys who are ready to open their hearts to them. We like good listeners. Try and make small talk with other girls. I'm not that keen on passive conversationalists so someone to speak to and make light conversation to is always nice.
I know it sounds really strange but you should try joing a drama group. Drama is a fantastic way to make new friends, who share the same passions than you. In drama hunkyness or "cool" doesn't matter. You have a laugh with everyone. I found love through drama, it's fab! I totally recommend it. And it gives you so much self confidence.
Did I mention the ability to make people laugh is good. The fact that you claim yourself to be mature shows that you understand that true beauty lies within. Those that are just passing you by and not speaking to you don't have real eyes and are not as mature as you because they don't see the real you, the true loving person which I'm sure lies deep within.
So keep who you are, make light conversation, develop an ability to make people laugh and get involved with a group self boosting confidence pastime, such as music and drama. Take it up, believe me it's fun, even if you are only working backstage you get to meet lots of new people who WILL appreciate you for who you are.
And by the way, to me you sound like a lovely person :D

OKAY don't try to change yourself to get girls I'm 14and I fell in "love" with a guy that I wasn't even attracted to at first. You need to act really sweet. You don't have to be boring girls LOVE a sense of humor. Do really nice and things for a girl you like. Also PLEASE PLEASE PLEASE never ever act differently around her just because your guy friends are there. So to sum up- be nice. Be funny. Ask her questions about herself (girls love to talk about themselves). Tell her she is beautiful, NOT HOT, but beautiful. Don't be afraid to put yourself out there. Help her out if she needs it.