Sorry to hear that you are feeling upset these days. The exam which is the most important is coming quickly. I know the stress of you is very heavy, but don’t be too nervous. It will make you worse.
You say the stress is very heavy to you and you can’t sleep well in the night. Then you can’t have a good health to study well in the day. You are very tried, the body even the heart. And the study is not very good.
But don’t worry! I will help you. You have to have a good rest to relax your nervous mind. You can go to park with your friends, talk with your parents or go shopping. These can help you feel not so nervous. After these, you go home, you can take a bath. Then lay in bad, close your eyes. Please don’t think anything. I think after a while you will fall asleep. The next morning you must feel good. Next time, if you feel nervous about the exam, do this. I think you will have a good score in the exam. Come on!