You need to get a black light, not the cheap one that comes with the Urine Gone. See if your vet has one you can borrow. Go around your house and shine the black line. Any urine stains will glow. Get Nature's Miracle or Nok-Out and spray the hell outta the stains. If the urine has sunk into any carpeting, you may have to pull up the carpeting and the padding. If you don't, they'll continue to pee.

I do hope you can get it under control. Please, PLEASE get your cat to the vet and rule out a UTI.

I used the spray Feliway for Buddy, who was having a peeing issue. It worked wonders. I've heard the diffuser isn't as powerful as the spray.