Do I have a purpose of living?

If you truly feel this way you could go and talk to your parents. They probably have no clue you feel this way. If you dont want to go that route, then dont feel so down on yourself. You are only 17 and it may not seem to young but it still is and you have plenty of time to figure out what you want to do in life dreams etc. Just always remember someone is always thinking of you even if you dont even know it. Good luck and I hope things get better for you.