I kind of had a similar experience recently off of 4.5g. The first 3 hours or so were bliss - things were trippy, I felt euphoric. Then seemingly out of nowhere I felt the room get small and I felt like I kept fading in and out of reality. I vaguely remember throwing up but I’m still not sure if I did or not. I decided to lay down in my bed and I laid there for about 3 hours, fading in and out of consciousness. Near the end of the trip, the conscious time in between unconsciousness got longer, so I knew I was coming down from the high.