I am worried about my cat Figaro. He is 5 1/2years old, and has been exhibiting a radical change in his behavior. He used to be an outging, playful cat. He would run and get his play mouse and drop it at your feet to throw and he would then bring it back. He would run out to greet us when we came home and want to be scratched and play. Now over the past month he has changed. At first he would just sit under the coffee table, then he took to hiding under the bedspread, then hiding in a cupboard and now he just sits under our bed. He will only come out when he hears you opening the sliding door to go outside and he will cry and cry to go outside. He is an indoor cat, although I take him out on occasion, in my arms. The moment we come back inside he runs under the bed. He is eating normally and using his litter box as usual. But he is not the happy cat he was 5 weeks ago. I don't know what to do. His eyes are clear and bright and his fur is fine. He did go through about 1 week of having hairballs, maybe 3 a week. But he is fine now. I brush him every day. Any suggestions??