First of all, let me say I saw your post and since I dont really celebrate xmas except just to enjoy the holiday, I thought I might reply.
First off, dont ever think that all is lost. Things can turn around quickly for you. You're only 23 yet and you have a way to go in life. And your problem is not unique. I am sure there are tons of people exactly in your situation. Its just how you cope with the situation. Some people cope better than others.
You are a special person. You need to find the right type of friends and those that truly like you.
Ok, now lets see. You said that at one time you drank to excess. Is it possible that unknowingly you say some things to piss people off? You might think nothing of it, but sometimes people remember such things and then try to distance themselves away from you. They might be scared you will say something that will make them look bad.
I knew this one guy at work. He was a true genius. A very talented computer programmer. When anyone had a problem they came to him for help. He was getting paid about a third of the average programmer because of his attitude. He would routine insult someones intelligence and people used to get pissed off, but his boss kept him around as he was a problem solver and highly skilled.
Thats the first thing you have to make sure you correct. Don't say anything to piss people off. The second thing is that you are a little too self-conscious. You think everyone is looking at you or that you are the center of all attention at a party. Dont feel like that. Just try to relax. Don't go out of your way to get people's attention. If possible, find a date to go along with you at the party. Then you at least will have her to talk to if nobody else. Be brave. If you feel nervous, try not to let anyone see it.
You know a lot of people at these parties are just as nervous as you are. But they dont show it or cope better than you. There are only a handful of people that are the true extroverts and dont give a damn about anything. Many people are just like you. Self conscious and worried about whether people will like their looks or their walk or style or whatever. The mind is a very complex thing. It thinks and worries about all kinds of things.
Dont let any of this stuff bother you. Just be yourself.
As far as looks are concerned, nobody is ugly enough that people will hate them just for being around. You mite not get too many dates, but your looks wont stop people from talking to you or being nice to you.
I have seen some of the ugliest people get a lot of attention. They might in fact even be the life of the party. So dont even think of looks being a problem. Besides, girls have to worry more about looks than guys. With guys, its the muscles and the way we carry ourselves that counts more.
I would suggest that you consult with a naturopath. Though I have never done it myself and dont know where to look except in the yellow pages, but I think if you explained your problem to him/her, you would be able to take some supplements to make you feel more confident. You might want to try a psychiatrist too. Make sure its not a psychologist, but a psychiatrist. A psychologist can't prescribe anything, just gets paid to listen to your problem and offer suggestions which I dont think will help you as much as the prscriptions from a psychiatrist.
Lastly, if I ever met you, I would not stare rudely at you. I would make friends with you and we would both have a good laugh.
Merry xmas and a happy new year to you my friend and pm me anytime.