((((((((Amber))))))))) Welcome to PC!
Honestly ... tell someone. Anyone. Whether it's your parents or other relative, a teacher, a friend, anyone that you trust. Are you in high school? You could talk to a guidance counselor, if you think that would be a good place to start. Or, if you'd prefer to go the anonymous route to start, what about calling your local crisis line? There are professionals there who can help you figure out what the best course of action would be for you.
I did not tell my parents about my depression right away because I was afraid of how they would react, and because I was afraid to admit to myself that I was depressed. So I told my best friend first, and she helped me get up the courage to tell my mom. Then, with time, my mom helped me get up the courage to see a doctor, who helped me get up the courage to see a counselor, who was able to get me in touch with a psychiatrist. Start wherever you can. Even posting here is a good first step. It doesn't matter who that first person is that you tell, because even if they can't help you directly, they may be the stepping stone you need to get you to someone who can. If saying the words out loud scares you and you think it might be easier to write a letter, do that. I know I am a lot better at communicating on paper than I am out loud.
Please do tell someone, and remember above all else that you are not alone in this.