It may be late to answer now, but to anyone in the future taking exams in a couple days, consider this.
If you feel stress before exams, that's good, in fact it's great because stress causes your brain to be more aware and keeps adrenaline on standby. This also means that your memory is improved by a large percentage, therefore studying now is not too late because you will remember much more than the usual remembering curve (if u know what that is).
Use it to your advantage, or if you really need sleep then do the following crazy thing: Turn on the shower, make it as cold as possible and just stare at it. Ask yourself similar questions: is it scary? Will it do any harm? What could possibly happen to me?
If you have met a realisation than there is nothing to fear and jumped in (even for a second) then you have shown self discipline and determination. You can probably guess its a good sign.
You will also use up some adrenaline and stress making you SO much less worried for exams, you will be more relaxed and will fall asleep.
Good Luck and tell me if you succeeded.