At the beginning he has been released from a mental hospital--he might think he was back there this whole time. I can fudge the timeline in a variety of ways. What I can't find on Google or ask.com is how long can someone have an entire hallucination? I find different types of hallucinations, sleep-diprivation hallucinations, etc. But nothing on longevity and possible causes (a doctor would make assumptions about what is wrong with him and it might be mental illness or something else).
I hope this makes some kind of sense. I need medical answers. Thanks so much!
PS - what are all of those "retags"? Will they be changed to something else?
ETA: Thank you! I am going to rewrite my scenario drastically. All of the answers were extremely enlightening!