I thought about what Snape said. But then couldnt Dumbledore have been acting since he was in the presence of Deatheaters? And Dumbledore probably didnt want to kill snape but knew he had too.
I didnt say this was a fool proof theory i just said it was a theory. Thanks for your thoughts. I still believe in my theory though.

Why else could he still be alive? Or why is it impossible for him to be alive?