How do I get my cat to stop peeing on things?

My cat has been in and out of the vet office recently due to urinary tract infections, constipation, and now slight kidney malfunctions (she’s likely developing kidney disease – but we’ve caught it early and are treating it). When she had her urinary tract infection and constipation she was peeing and pooping on the floor because, as the vet said, the act of going in her litter box reminded her of things that were bad (ie, pain) so she went elsewhere. I’ve since had her cleared up and she went in her box for a few days, but now she’s back to doing her business everywhere but the box.

I even tried moving the litter box to a new place and that seemed to work for a short bit. And when she came back from the vet in better health she went in her box for a few days but now she’s not again. Help! How can I change this behaviour?!