i wouldnt recommend this on a weekday, but on weekends try sleeping at around 8 or 9pm and waking up at 6am, this way you have an extra hour or two to calm yourself down and eat something, if you turn out to manage this sleep schedule, then you can use it for the actual exams. it might also help if you try to hype yourself up, also drink coffee instead of breakfast if you really cant, it should satisfy the feeling in your stomach for a little while.