He's marking your area -- letting the world know that he "owns" you. Neutered males and spayed females can both do this. The pheromone spray might work, but I also recommend closing the door to that room he is marking for a long, long time or you could try putting a small litter pan in the room that he is marking. Chances are he'll use it.

Sometimes changing the litter pan too much will cause this behavior also, ie: several times a day. He feels he needs his scent to show that he owns your house.

Believe it or not, sometimes having another cat will also change this. If they get along and bond, he won't be quite so possessive of you.