I once dissociated during an apointment and I saw everything in black and white for like half a minute, then it passed. I felt confused and also felt like I was in a movie rather than in real life, but I was still rational (no delusions or loss of reality) and knew the world wasn't really black and white or a movie. Other times I've had the feeling that I'm not real, but it wasn't psychosis because it was just a feeling - I was still rational.