Hey, I'm a girl. Hello to you from our kind!
You sound sort of Squall-ish from FF8. It's cute.
I was totally like you at one point. Here's my advice, for what it's worth. You don't have to like it, but if you follow it, you'll find yourself in more social situations:
1. Geography. When there is a group of people doing things, physically place yourself with them. Even if it's just a conversation circle standing around...you won't be asked to join. No one asks people to join. You have to move your body over there and stand with them.
2. Rearrange your mental conception of 'friend'. I used to be convinced that my only friends were the 2-3 people I felt like I was really REALLY close to. You have to switch it around so that 'friend' becomes a descriptor for anyone who is not an 'enemy'. Yes, that makes pleasant acquaintances friends. Go with it.
3. Smile and greet your 'friends'. If you know them and you don't hate them, say hi or just smile at them as you pass. You may feel like a poser for a bit, but just do it. People love to be smiled at.
4. Ask questions about people. I hate small talk, but it's the connective tissue of social life. So, when you say hi to them, ask them a question like "how are you?" If you know anything about them, like that they play sports or videogames or whatever, ask them about it. The best questions to make friends involve opinions. Ask "what do you think about blah blah blah...the new Halo game...the new boss...that homework assignment...whatever." People love to be asked their opinions. You'll make friends this way. ASK GIRLS THESE QUESTIONS TOO. Think of girls as boys with boobies. We are so similar...don't just limit your interaction to the 'hot' girls. Girls are very impressed by a guy who is comfortable interacting with all, from the nerds to the most popular people.
5. You don't have to give up gaming! It's fun stuff. Try games where you have to interact with people, like fighting or racing games. Stay away from online games for a bit. But gaming isn't the cause of your problem...it's only your crutch. And I love crutches.
#1 rule...if you don't feel it, fake it. Smile when you are uncomfortable. Greet people when you'd rather just run away. Share your opinions even when you think you're dumb. The more you fake it, the more you'll feel it. It's the faking it that's hard, but SOOO necessary. Faked confidence is only obviously faked to you. Everyone else just sees a confident dude.
Good luck, buddy!