Hm. "I am not getting enough sleep" implies that you are tired. That'll affect the efficiency of your studies. If you're not used to staying up late, I suggest not to do it. Lack of sleep deteriorates your ability to concentrate - so you may get some good hours done now, but that'll affect you later on today, and tomorrow.
Sleep as you normally do, wake up, study and take breaks.
I know there are only 8 days left, but try not to scare yourself as much as you can. It's 8 days until the first english exam. There's more than 8 days until your others. You can do a lot in 8 days without too much procrastination, trust me.
If you need anything, feel free to PM me!
Good luck.