Our momma cat came to us as a pregnant outside stray. We brought her in the house about a month ago and she used the litter box like a champ. Now, 4 days ago she decided to completely quit using her litter box. It was always kept clean, so not sure why she quit using it. We found where she was going potty in the basement (on an old towel?!?). We cleaned it all up, and have now locked her in my daughters room where her kittens are (normally door is open so she can come snuggle with us whenever she wants). Any suggestions on how to get her to start using the litter box again?