I am also many, many years your senior. Unbelievably, I only recently became aware that, if I had not been so much in a shell at your age, I would have described myself just as you described yourself. I cannot tell you strongly enough that you absolutely need to get professional help. You don't think you write well, but you have clearly articulated your mental health status. A qualified counselor will give you the necessary tools to understand how you got to where you are and how to navigate beyond this point. I don't know anything about UK schools. Is there a counselor on staff you can go to who can help you locate a therapist as well as communicate with your parents?