I want to get my life back on track but for some reason I don't want to.?

I have exams next week, really important, deciding factor for me getting a scholarship of �3000 and potentially a place at medical school but for some reason I dont feel like looking at my books. I'm also very unhealthy and unfit, just like watching TV instead and eat lots of ice cream. I can see the benefits of making a start to get something out of my life but then I easily give up, in the past I have made several efforts each time I make a start such as exercising, eating healthy and studying I give up after a few weeks really easily and then put weight on again and my hard work seems to go to waste and then in the future I become more and more reluctant to start again as I don't see the benefits. Does anyone have any motivation tips for me? I would really appreciate your help.