Well... at the moment he seems to like Whiskas again, but only 2 kinds and only very little. He's not loosing weight and seems to hunt all day long. I tried baby food, but he didn't want it either (the dog did though).
It's so hard seeing him sitting at the table where he's always getting his food and he won't touch it.
I'll call the vet and ask about the Hills prescr. diet food. It's worth trying it. Thanks!