For the last 2 day's our cat all of a sudden stopped eating,drinking and playing & just an hour ago sipped a little water, but lies down all day and has no interest in anything, but when I pet her she lightly purrs. Why do they have this behaviour all of a sudden. she goes out at night mostly but lately because of the cold wheather she stay's inside mostly. I would need some answer's before I go see the VET $$. Thank you!!