My cat Lilith is usually a very good kitty but for the last few days she has not been very good. I was gone off and on during the holidays and I'm not sure if that is why she is upset or the fact that she is usually allowed to go outside and the weather has been too cold and she has to stay inside. She has been an inside cat before and I never had any problems with her. Now she is using the tub as her litter box even though her litter box is clean. What can I do?