I believe that, as most people in this thread said, you don't have a problem with introversion or extroversion. I think the problem is with social skills.
I had this kind of problem too. What I did is I read a book by Dale Carnegie entitled, "How to Win Friends and Influence People" and started simultaneously applying everything after every chapter that I've read. I still haven't finished that book yet.
I'm still working on my social skills. What I've been doing since is hanging out with all the people and you'll learn a lot from hanging out with them. But, you should always remember to be just yourself; you know, it's very cool just to be yourself. Don't pretend and don't fake yourself so that other people will like you. They'll like you as you are. Sometimes, they wouldn't like some part of you, but as you hang out with them much, they will automatically accept it and you'll be all fine. Try it.
I used to pretend and just be quiet so that people would like me. It was a hard life for me for faking myself and not doing the things that I want. So, you have to work on being yourself and standing as you for all times.
