Try to say more about the problem. It's a rather vauge problem, and we can't see much out of it
You need to see a doctor, many teenagers suffer from depression. At 17 years old you shouldn't be feeling sad long term. There is medication to help you and nothing to be ashamed of in asking for help, it's an illness just like any other.
I am so sorry that you are depressed. Have you tried talking to a friend or a trusted adult about your feelings. They may be able to help you sort things out. Have you tried prayer? Give a try, it works. One thing I've come to rely on is that God will never tell my secrets. He always has a listening ear and most of all he always has time for me. The bible tells us at Psalms 34:18: " Jehovah is close to the broken hearted, He saves those who are crushed in spirit". Jehovah knows your feelings and wants to be there for you. I hope this is helpful to you. Another thing I would try is a doctor. It could be something hormonal that they can help you with. Feel better soon.