You seem to suffer from examination anxiety. You need to learn stress management techniques, such as deep breathing and time management. Do not study too much just before an exam. Start preparing for the exam ahead of time. Try to learn the lesson in short points after understanding. When sitting for an exam, take deep breaths before reading the question paper. Spend 2 minutes to read the paper well. Tell yourself that you can answer well. Stop repeating to yourself that you do not remember anything. Start writing any answer that appears to be easy. Take one step at a time. You will soon find that you are able to tackle all questions well. If you do not improve, consult a psychologist or medical doctor.