Welcome,
You aren't alone. I don't trust many people either&tend to isolate, maybe you have social anxiety disorder-though I think going to the anime convention was a good first step. Keep in touch with the people you met&let it slowly grow from there.
Stop beating yourself up! You're not stupid or garbage&screw the kids who dissed you in school&in your home town. People are cruel for the dumbest reasons! I know what it's like to have a hard time meeting people-I isolated until the only person I had was my bf&when things got bad there I was really screwed. We've since patched things up for now. My family is another story-they treat me like a pariah because I'm mentally ill. Screw them!
Have you tried to make friends with people you work with or by volunteering somewhere? Another place you might try is a website called meetup.com, they have groups local to many metropolitan areas&have groups that meet for lots of things-social, things in common, support, etc. I've met people through that website&have had pretty good luck so far. I go to a self esteem building group now. Check them out.
Best of luck in the New Year&feel free to PM anytime.