We got our new cat on Saturday. He is quite shy and timid but affectionate. He has spent most of his time upstairs sleeping on my son's bed, only venturing downstairs to eat. I've put a litter tray in the downstairs bathroom which he has been using, mainly at night. However, for several days he has also gone into my bedroom and pooed on the bed. I'm getting desperate and on my 3rd duvet! I'm sure it's because he's nervous coming downstairs but don't know how to help him. Any ideas?