My 5 yr old little boy is urinating in inappropriate places

My 5 yr old is also urinating in inappropriate places.  I've read several other cases here on this forum with the same issue.  The only commonality that jumps out at me between these children seems to be that they're all, or at least the majority are, underdeveloped somehow.  My son was 2 months early.  He is developmentally about 6 months behind his peers.  Could this be some Fruedian desire to remain a baby?  I'm at my wits in.  Last week he decided urinating on the hall stairs would be fun.  He soaked the first three stairs.  This morning he promptly got up, and went into his toy room and peed on another one of his carpet squares.  (Thank goodness they are carpet squares!)  He pees outside when I'm not looking and the worst was last week when he peed in the middle of my bed!  Tips please!  This is unacceptable!  Now when guests come over, I'm afraid that I haven't got all the smell out and the house smells like a cat box.  Ah yes, the cat box; another of his favorite places to pee!  He also defecates there and does that outside also.  


This discussion is related to Behavior problem of Urinating on Toys and Carpet.