If you are shy now then you'll still be shy when you go to university so don't see that as a magical answer to the problem.
Being shy is more a state of mind, teach yourself to be more self assured. When you're standing in a queue or something, strike up a conversation with the person next to you. Something about the weather is always topical, or maybe how long you've been waiting... anything, but speak to a stranger.
Look around for a club to join, there must be something you've always wanted to do. How about joining a local theatre and help behind the scenes, painting sets or helping with make-up and costume. I know from experience that this works, they'll jump at the chance to get support of this kind and it'll do wonders for your confidence. You will surprise yourself too, you'll start wanting to be on stage yourself, even if only a walk on part, and then the lead will be tempting you. Whatever the outcome you'll make friends.
When you go to uni make sure you join societies or you will end up hiding away in your room.
You can do this, believe in yourself.