The thing is, why do we need to assume it has had to "come" from anywhere? I assume everything has always existed.
I don't see it as an own reality, but it is how we perceive the reality. I shouldn't even trust our own consciousness either, as we as humans have mechanisms which make us untrustworthy even for ourselves.
We can't trust our mind, senses or memory perfectly. We have only a limited view on the reality and the consciousness is disturbing on it too to protect the mind and to fill the gaps in the senses.
I do not believe as you do, kept in short regarding McKenna and other mystics. Even though what you believe, she doesn't seem to have very much knowledge regarding the Big Bang :)