I want to offer my suggestions here for how to go about this; as I've noticed nobody here has yet responded to the question, but there are a lot of you feeling this way.
Until a year ago, I was exactly the same, due to various things during my childhood. I couldn't talk to anyone and had no friends.
However, towards the end of last summer I just told myself that I was going to change, and, although that sounds like it wouldn't do anything, it did help. Changing your state of mind is the answer. Instead of thinking of yourself as shy, force yourself into situations that scare you.
For me, this started as staying in the Sixth Form at lunchtimes instead of leaving due to my nerves, meaning that I was surrounded by people at a time when I had the potential to talk to them, and slowly I became more accepted which then boosted my confidence. Over the summer, I went to the pub on my own in the hope that classmates were there, and if they were, they let me sit with them which again had the same effect.
This increased my confidence at first, and from then on I chose to just dive into any social situation I could; now when I meet a new person, I don't approach them as though they're someone I've not met - I find it easier to meet a new person by pretending that they're already my friend - I talk to them as though I know them already, without asking the basics, and these facts fill themselves in automatically in time - it's easier than worrying about starting up a new conversation.
I'd now consider myself a really confident person; I've lost all the shyness I used to have, and I'm continuing to push the boundaries socially to make this go further.
I hope some of that helps; because just because you're shy now, there are ways to change that, it's not an inbuilt thing.