I don't get american psycho

I don’t know how to do the spoiler tags so i’ll just drop this way down

What happened at the end? Did it turn out that Patrick imagined everything? Did his dad cover everything up for him? I know Patrick lived half in reality and half in his own head (for example, he’d ask his secretary to wear a skirt but in the end of the movie she is wearing pants like she always does) and the ATM machine never asked him for a cat and a handgun can’t blow up a police car. Plus before he killed Paul Allen he took a pill which may have been an antipsychotic. Plus when he was arguing with that Chinese woman at the laundromat he said in english ‘if you don’t shut up I will kill you’ even though before and after that she couldn’t understand any english whatsoever. So I assume some of the movie was just fantasy.

However in regards to the laundromat situation, Patrick still had blood on his sheets. I doubt he had a fantasy within a fantasy, so he actually killed at least one person. But how did he get away with it? Why did the people in Allen’s apartment cover up for him after they found out what he’d done?

My rersonal view is that Patrick murdered the street Bum, but everythig else was fantasy. The bloody sheets were his immagination they were probably just dirty, no one would take very bloody sheets to a Laundry too many questions might be asked. I think he fantasized about the murders and the prostitutes. It was ultimately about the emptyness of his life and a moment where he took that out on the street bum only to be pushed over the edge into insane fantasies but not I think murder.