Thank you fir asking. I can understand your distress. Your complaints are clear cut suggestive of stress related anxiety problem. In your case the pressure of performing in exams is the major stressor seen. You must understand that it is a normal phenomenon. It is temporary phase and will pass on. Also, you must understand that it is normal to not perform well in exam, it is normal to fail and score less. Not always it is that one will score high marks. It is normal. You must convey your distress to your parents and insist them to show you to a counsellor for stress management.
Next Steps
For specific answers, you can consult me directly here on Practo. A detailed information can help me give you specific suggestions.
Health Tips
Do not worry. Kindly see a local psychiatrist or counsellor.