I feel nervous in exam period, i feel like vomiting and sleepy.why is that?

You have anxious per: Some of us are anxious by nature and get even more so in times of stress like taking exams. You have to learn to relax and cut down stress in your life. This will require lowering your expectations a bit, relaxation exercises daily like a good walk and take advatage of yoga and or meditation which can teach you how to relax(proper breathing exercises). Find a supportive friend and supportive paren.