One advice to anybody who hasn't spent much time thinking about these things deeply before. Don't do this alone. Have somebody with whom you can discuss (not on computer). Your mind can become like a shifting sand and you won't have any sort of hold to understand the world. Which can be extremely disconcerting.

You have a world view that you have acquired/formed based on certain assumptions that you may have never questioned. Once you start questioning them, you won't stop at any assumption, and you go into a sort of mental abyss, especially, if you have never believed in God.

One consolation is that however hopeless it may feel when you go there, you'll probably come out and get back to your usual self.