As u/crimsonchinkapow said, be honest. Write it out if you have to, just to organize your thoughts. But talk to your parents. Share what you can. Let them know that there's more you can't share. But that you are asking for help. You can also go to your school counselor and get help from the school to meet with and talk with your parents. Sometimes keeping it in the family is the right thing. Sometimes having outside support and mediation helps. Only you can decide. The school may also be able to put your family in touch with therapists / resources. It's nice to have a roadmap when you're trying something new like therapy. Someone to point you and your parents in the right direction.