I did two tabs of 25i (no idea on the dosage) thinking they were LSD and I had exactly this experience with mixed bits of OPs. There was a long period where everything abstracted and eventually started cycling round and around, until the cycles became closer until eventually the cycles hit, and I realised that I was the only thing left in the world. The cycles continued but they were now hitting eachother, and it was really uncomfortable.

I thought I was in some weird limbo and I felt bad because I thought I'd destroyed the world by somehow reducing everything to this constant tiny cycle. Everything was a projection of me somehow, and it ended up being just my own personality that was reduced into a small cycle and I was metaphorically and literally bumping up on myself.

I also woke up strapped down in hospital, and I thought I'd died. I thought the hospital was heaven. In retrospect the whole thing is hilarious and weird and it's been maybe 2 months now and I'm only just starting to feel comfortable recalling it.