I can speak from experience on this. I am an introvert, not much of one, but one nonetheless. It's been measured by Meyers-Briggs. When reading this, just keep in mind that being an introvert is not a fault.
We introverts have gotten by somewhat happily without the need for a lot of interaction and our social skills have suffered as a result. This is a problem for us in our dating lives, because our lack of social skills makes us deficient in the most important area: courtship. Once we're in a relationship, we're probably okay.
For the most part, once an introvert, always an introvert. Introvert doesn't mean you're boring or uninteresting. It just means you don't NEED people to be satisfied, or for validation. You're generally okay being alone; you can entertain yourself. And unfortunately, the cold hard truth of being an introvert is that you will have to work extra hard, ALL the time, for ever. But if you are mentally tired of the way things are, and are prepared to do the work, it won't matter.
Secretly, we WANT to be around people, because getting validation makes us feel better about ourselves.
So what to do? Here's what I've done. FIGHT IT. Get a wing group together, and share the sh!t you can't share with your friends. Be accountable to each other. Force each other to go out and practice when you're feeling anti-social. So when you start feeling over-stimulated like a cat, and like you don't want to be around people, they'll force you out and eliminate your ability to make excuses.
Start taking classes like storytelling, improv, acting, dancing... so that you'll feel better about yourself when the social fears seem to be at their strongest. TRY to have FUN. Do EVERYTHING for your entertainment... even taking something like "rejection" and trying to make it as funny as possible. Laugh every time you fail. So get out of the house, be an amazing man, talk to a lot of girls, bomb lots of sets, toy with your own mind as much as you are there, be an amazing man, and live. I said the amazing man part twice on purpose.
Get it?