PLEASE speak to your parents. I am a parent myself, and I can assure you that I would want to know if my child were suffering and having thoughts like this. This sounds like serious depression, and there is hope and help out there for you.
Do you have a trusted adult, other than your parents, who you could speak to? A teacher, or a counselor at school? They may be able to help you get started before talking to your parents, and can help you with ideas on how to approach your parents about your suicidal thoughts.
Please don't go through with it. You have other options, and a family who certainly cares about you.