I failed some of my exams?

I'd say you have to relax a little. Start studying earlier, and one day before your exams start, stop studying and go out to do something you enjoy. Get a good night's sleep. You could do your own additional reading online or at the library besides course materials. Write out your notes immediately after the lessons so that you retain as much as possible. For math, practice! That's the most effective method. You can buy assessment books or search online for more problems to do. Get a tutor, if you can and are comfortable with doing so. As for your parents, they may be disappointed, but remember they'll always love you, no matter how well or badly you do in exams. They want you to be happy :D