Man Claims To Have Been Michael Jackson's Gay Lover

Jason Pfeiffer -- who once worked as Klein's office manager -- tells TMZ he's sticking to his story -- that he had a sexual relationship with the King of Pop -- despite Dr. Klein's recent Facebook post, calling MJ's gay affair a lie.

Jason insists, "The story is true. We had a relationship with sexual aspects, but I'm not going to make it into some grand love affair."