100% positive there is no God?
Well, no - but, I'm not 100% positive about anything.
I'm fairly certain that all the "deity" and "creation" myths are just really myths - as most of them are simply absurd and have no supporting evidence.
As to "proof" - ultimately, one can only "prove" mathematics and gain evidence for the existence of something. You can't "prove" something doesn't exist, you can only gain evidence for it's contrary.