Completely relate to this! Did you reach the brink of death of your consciousness? I did, and it was a strangely blissful process involving flashbacks from important experiences I'd had in my life. Total sensory stimulation was aroused alongside these flashbacks too, i.e. smells that I had long since forgotten came back to me, and it was so natural and calm. Then brief panic which left a resounding dread feeling at the certainty my mind was getting ready for the big sleep. But instead of my spirit departing my body and my mind entering its big sleep, it didn't, and I was left with what you described, utter existence in its purest form, just my spirit - and this was were much self-assurance and self-insight was gained.

There were no entities that people often speak of, just indescribably potent visuals and flashbacks, and as close an experience as is possible to death.