I know how you feel man. I went through something pretty similar when I was in high school.
You mentioned that you don't see any purpose in life. The mere fact that you are asking these questions, and looking for deeper answers says alot about you. Many people are quite sattisfied to live a very superficial life. Once one begins to question the purpose of the seemingly thoughtless loop that many people live out, it is only natural to become a bit concerned about your sanity.
I'm sure you've had moments where you've even wondered whether it was you or everyone who is totally insane. This is a good thing. Without asking such questions in life, you are simply accepting life on everybody else's terms.
It was the truly great souls who questioned reality, and therefore, by asking, eventually found what they were looking for.
The interesting question becomes, ok, well, now what, right?
Does any of this make sense?