Naughty sexual monster...iin?

I have a 13 year old son who has always been awkward and has imaginary friends. Recently though he has been getting me up at 11:23 exactly each night to tell me that he thinks something is under his bed. He says that the monster whispers to him that it wants his cock and wants to ride it like bull. He says that he tells the monster to go away but it doesn't work. When I go into his room to check there is never anything there but he swears he hears banging throughout the night from under his bed. He tells me that he constantly hears deep breathing and moans. I am afraid the a petifile may be after him. Is this normal?