I tend to get nervous before exam and this screw up my marks in exam. any advice so that i can be more confident and relax before exam.

Common problem: It's not always appropriate to use medication for this anxiety reaction. I have found that a consult with a psychologist (PhD.) or a psychiatrist (M.D. or D.O.) is the best remedy. They will teach you how to cope with this universal problem and it can be really helped without medication.

EMDR exercise : Look up EMDR eye movement to rapidly decrease anxiety. Basically you are going to rapidly move your eyes in different directions for 30 seconds. This helps your brain process and disappear the anxiousness.

Performance Anxiety: Performance anxiety is a very common occurrence, especially before test taking. Progressive muscle relaxation is extremely helpful in relaxing the body. Meditation helps calm the mind. Cognitive Behavioral Therapy can help challenge erroneous beliefs. There are also medications that you can take beforehand to settle down the autonomic system which is highly activated in anxiety states.