Hey hey, don't think like that!
Seriously, that is a dangerous spiral to go down - you are only 17, you have another good 10 years to go on the youth side of your life, and there is plenty of time to get into the whole swing of the social scene.
There are no definitive cures and guide one can follow to lead themselves out of the situation, but I'll try and suggest some things you can do which could help.
I think first thing you need to is to build up on self confidence, which is easier said than done. Try and edge yourself to do some simple things, ie, talk to your classmates more, try and engage in a deeper level of conversation with them rather than just your daily classroom talk (ie, did anything fun this weekend?, up to much recently?). Get in touch with your current friends, even if they aren't that close, and ask them to hang out - go shopping, film, see a play, whatever takes your fancy.
I'm not sure if this helps at all, but watch some stuff like One Tree hill, OC, Gossip Girl, general teenage shows - for two reasons. One, maybe you could just pick up on some hints on the general social convention and how to act etc, and secondly they are decent conversation breakers (you seen the new Heroes recently? etc).
Join some societies, very simple ones, like maybe a film group or a discussion group. Find similar minded people, that likes *you* for whole you already are, rather than those who like you because of superficial reasons like your looks. Maybe you find it could help joining a social networking site for exposure to meet more people, ie Facebook.
And realise that you are about to turn 18 - and if you already don't - GO OUT! Clubs, Bars, lots of places open up to you when you are 18, and approach them with some confidence and self belief, and you could make some new friends, take their number, ask if they'd like to go out next week (boy or girl) - don't rush into a relationship (unless you really feel its right, take your time).
Drink a bit, you have less inhibitions and you are more talkative, but drink responsibily. You could even do simple stuff like find someone nearby you on TSR that's interesting, talk to them for some advice, meetup etc etc (but be careful, of course).
That's just a random blurge of advice, but take them with a pinch of salt because they are really hit and miss things (some would find they'd work, some would say a waste of time), but they are just some personal advice. If you need someone to talk to, feel free to PM.
Hope that helps
