Sometimes simple changes can cause a cat to pee in weird places such as changing the location of the litterbox. Star was used to the litter box being in a particular corner and we rearranged the room but she continued to go in that corner regardless, then she got used to going outside so she become potty trained to going outside. Sometimes stress, like the holidays too. Like the previous poster said, I'd call the vet to rule out a UTI too.