I'm a sixth form teacher, and often come across students who feel as you do. It sounds to me as if you are suffering from total exhaustion.I think you need to replan your life, making sure you are eating properly, getting some exercise, and getting to bed much earlier.I suggest working for short spells, say half an hour, then taking a break for fifteen minutes to have a coffee, talk to a friend or the family, walk round the garden, listen to some music. Then get to bed at eleven ! I have a feeling there's a bit more to this than meets the eye. Are you at all depressed ? Is the family concerned about you? Should you have a chat with your doctor ? There are few university courses more stressful than medicine, and you need to get this sorted out now, or you'll burn out in your first term. Do get back to me if you'd like to talk any more.I know that the lifestyle changes I've suggested are not easy to put into action, but please do give them a try.