My cat was spayed years ago and every so many years I would see little spots of pus/blood where she squats. She like to find things like boxes or towels to sit on. Three years ago when she had the pus/blood it lasted for a long time and was bigger spots. I took her to the vet and they ran all kinds of test adn foind nothing to be wrong with her. No infection or anything. I took the wool rug in the one room aways and she stopped the pus/blood. Well a few months later it started again. WIthin the last few months it has gotten to be large pus/blood spots and it is more frequent. Do you know what it could be caused from? Thak you.