Maybe it's the lack of objectives that makes you feel like this, have you ever thought about this ? ....I'm afraid I can't help you much if you are not a little more specific though .
It sounds to me like you would need a litte extra help from a specialist, because it seems that you can't really tell what the real problem is and why you feel this way.
A specialist would be probably able to identify the real reason behind these feelings during therapy.
In the meanwhile try to talk about this with your parents .
Do it seriously.
Make them sit down, tell them what you are feeling and that you need help, suggest them ways they could make you happier, it could be more effective than you think.
Anyway since you said
"I know that I have much to be thankful for and happy about but im not."
Try to watch this I think it's very ispirational
I wish you the best.