How do I get more confidence?

I had to go through the Air Force to gain my confidence because I was the very same way as you when I was back in high school minus the small part. Confidence comes through achieving goals in which you really start to believe in yourself. Go do something that you can be proud of and can talk about. Oh, and most importantly learn to laugh at life. Never take things seriously and develop a good sense of humor. Positive energy is so contagious that people will flock to you like moths to an open flame. Good luck bud. If you need anymore advice feel free to message me, I'm kind of an expert on this topic really now.

I'd suggest finding a clique to fit into. In order to do this though, you need to venture out of your "old comfort zone" and enter your "new comfort zone. "
Try out for a play (school or community theater) and sign up to be in the Pit Crew. Then even if you don't get cast in a role, you can still hang with a new group of people.

Whatever your passion is, go for it. Find something that you love doing and just branch out and find who you really are. Communities of almost every size are accommodating to different groups and societies, and activities that you can engage in. Find someone that shares similar interests and start your own community group.

Social events will be nightmares and will only hurt your self-esteem unless you are comfortable with them.

A final thing.
Though you may be in a new area, just remember that you are who you are. Don't change to fit into your new "society" be it school, work or community at large. Remain who you are, and be happy with yourself. Others will be compelled to like you for that.

I would like to help, but before I can, I need to know these things: What type of interests do you have? Have you got any talents? What are your goals? Like say, if you're a singer, you may want to join a local Choir, go on auditions. Maybe you can join a dance or an art class. It all depends on what you're in to. I always find that you'll meet great people doing something that you love doing. Force yourself to come outside of your comfort zone -- you'll find very nice surprises about yourself soon after.