I'm so good at pretending that I'm not sure anyone would believe me?

There is nothing selfish about discussing these very serious thoughts with your parents. They would not want you to feel this way, they love you. You are obviously suffering from severe depression. It won't get better without help. You have been very fortunate in that you have been able to keep your grades up, that certainly is something to be proud of. But this is a serious issue that has to be and can be fixed. You have to have a psychiatrist who will make the proper diagnosis and there are many safe medications that will help you. Depression is a disease just like heart disease or diabetes and requires medication. You have to get help you don't deserve to live like this. Please take the next step and discuss this with one of your parents and don't leave out any details they must understand the seriousness of this. I wish you the best!!