After many decades of battling schizophrenia I have learned to separate delusion from reality mostly by having a huge respect for rationality, logic and reason and being a seeker of truth. If things don't seem to add up I place them under a microscope and look for the weaknesses or flaws that contradict reality or what I know reality should be like.
My type is Paranoid Schizophrenia. On top of that I'm bipolar and have DID with two four introjects so, fantasy vs reality is something that I continue to question within from time to time. Being observant and analyzing your perceptions and memories will help you to get to the bottom of things.
Just stay calm and focus your mind on separating fantasy from fact.