Once on mushrooms, I encountered the mushroom god, and I realized that fungus wasn't some humble lowly plant-like lifeform, but a raging fire that consumed the planet. The God revealed only a small portion of it's glory but that was as much as my mind was capable of perceiving. Also, it gave me some relationship advice.
Another time, on Salvia, I suddenly penetrated a film between our reality and theirs. There were more than one there, primarily a female God, but another voice that commented too. The gist of what they said was- Hey, look at that, we are seeing more and more of them these days- they don't take it seriously enough. Then I was commanded not to use salvia any more, or promote it for recreation. This encounter lasted a short time, after which I was ejected from this space, which I seemed to have entered headfirst about to my neck. After that I was fused with the wall for a bit and then I was caught in a reality vortex, and a few other things. I came down a few minutes later and flushed my stash, I stopped shaking about two hours later. I kept my Salvia plant alive for some time after that out of respect, but I never smoked it.
Mostly I think it is impossible to believe in God. It's so outside of our reality that there is no way to call it real or not. And it's nature is such that we cannot comprehend it, so if we do believe in it, we don't really know what we are believing in. It's possible that they were generated by me, that is the most likely explanation, but the power of the encounters are still strong. Maybe sometimes your brain tries to tell you something, and the only way you will pay attention is to give it the appearance of a personality. In any case, there was no evidence to lead me to believe these entities had an existence outside of my own mind.