I work as a courier driver for Royal Mail, the contact I have with others is minimal, I spend 95% of my time driving and I LOVE it! The only time I speak to people is when I deliver a packet, or go into a baker shop for a cup of tea. I'm like you in that I don't like to interact with others much, but it's not shyness with me, I'm just finished with people sort of thing...I'm not recommending you become a courier driver though...
I think you would do well to get a job in a bar as a barmaid! It's fun and you will be forced to be sociable with people, you'll overcome your shyness in no time! And you'll feel VERY happy! I guess you might find it hard but I'd work in some place where you are forced to be sociable, you'll be amazed how happy you'll become!