I think you should go to the doctor, because you might actually have a stomach infection. For nausea, you can buy tablets over the counter (I have to take them all the time for my dodgy stomach) which really help and take away the sickness. Make sure that you're getting enough sleep.
I know it's really difficult, but you just have to get stuck in and start trying hard to enjoy yourself. Nobody tells you before you leave just how difficult it is at first, but let me reassure you that you are not alone in feeling this way.
If you're awake in the night and can't sleep, try Nightline - it's a national organisation, with a free centre at each uni. You can chat to them and they will help to reassure you.
Try to get to know the people on your corridor, just by going out with them, chatting in their rooms, watching DVDs etc. It will get easier and easier as time goes by, I promise.