My initial response is that you should see a doc ASAP. That said, and as you've already made an appointment, here's the 'good' news - you could be suffering from stress
. Stress, if you don't give it a way to vent can produce physicial symptoms and can kill you if untreated.
However the treatment is simple - find a way to reduce the stress. There are a number of ways to do that, for example you might try meditating, in this case until you see the doc I wouldn't suggest exercise. Check with your univ. library they probably have a tape/CD which will help you mediate. If the doc gives you a clean bill of health I would suggest you take up walking, it helps you physically and is also good for stress - get away for the computer and the books for an hour a day. You may even find that your grades increase.. 8^)
Good luck and remember finals will be over soon!