Peeing on the bed
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A UTI IMO would be the best case scenario, some antibiotics and bam situation resolved. Changing behaviour is a hard thing to do, it takes time and effort.
Having your animal checked for medical issues first is what ANY good behaviourist would suggest when there is a signifigant change in the animal. It makes sense. BTW drinking a lot of water would also make me recommend going to the vet first.