My cat (9 yrs old) has been extremely clingy to me over the last 10 days. He won't leave me alone and he can't get close enough to me half the time if he can't get on my lap. We've noticed that in this time his appetite has gone and today I've noticed he's walking very stiffly. He's normally very active, catching birds and mice but now he's barely going outside. About 2 weeks I noticed he was sort of falling in through the cat flap with his back legs but thought nothing off it. Now he's stiff today and even more clingy (if that is at all possible) I'm getting a bit worried about him.