Just like everyone else has said, holy fuck. IF you're being truthful about those 20+ gravity bong rips...

You went way fucking overboard. Even the most seasoned among us, with tolerances acquired from years of everyday smoking, wouldn't need that much to get baked as fuck. Usually, a gravity bong hit done right is the equivalent of a few good bong rips, so wow.

Marijuana IS classified as a hallucinogen, so what happened to you is not abnormal. It's to be expected from an utterly inexperienced smoker, whose tolerance is at ZERO, pretty much, who smokes a large amount of weed using a gravity bong, for Christ's sake.

I hope you're not turned off by that experience. Extremely high doses like that can certainly be unpleasant, especially for a novice smoker. I recommend trying it again, through a bong or a pipe, and only taking a few hits until you feel fantastic.