My cat will not stop pooping outside her litter box??!!?

So my husband brought home this kitten, at first she was pooping everywhere but I slowly trained her to at least poop in the room with her litter box. I've tried everything, I'm a housewife so I've cleaned up the litterbox after EVERY time she's gone in it but she still proceeds to poop on my floors, she also NEVER buries or even tries to bury her messes. I've talked to my vet, wondering if maybe it could be a UTI and she's ruled that out and said I just have to keep trying. Is there anything else that I can try?? I'm desperate