Dear Jack,
I am sorry to hear that you have some problem with your study. It doesn't matter. it happens that onw may have his blue days sometimes. I hope you can be confident in yourself and always believe that you can do better. Try to spend more time in maths and history,if you are weak in them. Failure is the mother of success, isn't it? Don't lose heart. Things are going to be OK. i trust you. Anything I can do for you, please tell me.
Love,
Liu Jun