I too used to be be quite shy. Actually, if I'm truly honest, I'm probably still as shy as I used to be. 

The thing that changed for me is that I've learned how to push past my shyness. I'd compare it to quitting smoking actually. You feel like you might just die if you can't get that cigarette, but you know full well that the opposite is actually true. 

Similarly, you might not feel like you can interact with others because of your shyness, even though you know that it might be fun to do. So you stick to your comfort zone. You light another one up again, because there's always tomorrow right?

What I'm trying to get at here is that it's not easy, and it might never feel comfortable to you, but if you try hard to fight it, it will get better. Don't hold off, start now. Try interacting with people you don't know well more, be the first to say "Hi" and get a conversation going. 

I wish you all the best of luck, I'm sure you'll do it! :)