HELP I NEED HELP ......................Dont know whats happinin?

I dont know whats happining, I just try my outermost socks off to obtain success. I' m one of the most dedicated persons you will find. I try my outermost to please family. when it comes nearer to exams, I some times dont even go to sleep. ( I be workin all day on my exams revisions, doing ignments ) but yet again I dont get the resuls I was looking for .however When I go into the exam my mind goes blank I cannot remember anything, and i dnt get good results.I think to myself wats the point of putting all the hrs whn you get low marks. I just dont know whats happinin, I think to my self shall I quit higher education, and now im in depression mode. I just need advice on how I improve my perfornances ?? whats the problem?.