Well when you're going at it from that angle, how can you prove to yourself that anything you experience is real? There are centuries of thought surrounding epistemology, I don't see why problems of how and to what degree we know what we know should apply to drug induced experiences and not regular experiences.

But then again, I don't know what you experienced. The most profound insights I had make perfect sense to me now, and they mesh with current scientific understanding as far as I can tell, so I have no reason to doubt them.