You should go to your school nurse, counselor, advisor, principal, or one of your teachers. Surely if you put forth the effort to try to get help, someone should be willing to help you especially if they agree that you may have a problem. They may suggest you try tutoring to begin with - it couldn't hurt and may be that you just need some one-on-one, a little extra help. Maybe they can speak with your mother and try to persuade her to have you evaluated. It's good that you're concerned and want to help yourself. Good luck!