I think, but I don't exist

It is just like a movie,
but I am not watching,
I am not acting,
I see everything passing in front of me,
but I am invisible,
I can't feel the touch,
I can't feel the love,
but I feel the pain.
I must be alive,
but I am not,
and I am not dead, either.
I am just trying to understand,
If I think,
I should exist,
but I don't,
I don't!