Make list of all the things you need to do, and work through the systematically. Try not to stress out: you'll get it all done if you organise your time.
It doesn't really matter if your hair isn't looking its best, today. And the pain in your chest and the lack of sleep are probably both caused by and contributing to the stress. So have a sit down and a glass of cold water, and relax for a while before going back to the revision.
Plan yourself little breaks, as well. Make sure you drink plenty of water, and put on some relaxing music (or something upbeat to motivate you, whichever you prefer.)
Just don't panic. Take things one at a time, and stay calm, and you'll be fine.