Dude, it's great that you know what you want to do for the rest of your life and all but you're pushing yourself WAY too hard. Eminemaniac is right, it doesn't matter how the other's do on the exam as long as you do your best. But while it's important to study and take the exam seriously, don't make it the only thing in your life. Make sure you do other things besides study or else you'll just burn yourself out. It's like if you were boxer, you don't want to physically peak BEFORE the fight, you want to gradually get into shape and make sure you peak when the fight is about to happen. So instead of running 5 miles a day, or sparring 4 rounds a day, you'd run 2 or 3 miles and spar 2-3 rounds instead so that you don't overwork you're muscles. Studying is the same way. So take Eminemaniacs advice and make a study schedule and make sure you have time to relax and do other things you like so that you won't be stressed out. Afterall, what's the point of having all that knowledge if you're too stressed out to use it?
I wish you the best of luck on your exam and hope you'll feel better soon