My pup is just shy of 11 weeks old now. We have had him for 4 weeks, and ever since we got him he has, of course, been after the cat (who is 3 years old). At first it was not bad, they were mutually playing and it was ok, but now that the pup is getting bigger than the cat I am worried it is not going away. After the first week we decided to keep them separated in hopes that would help stop the play fighting, but unfortunately it really hasn't helped. Whenever they are together the dog is always, always, always, trying to play fight with the cat. If we tell him no he stops, but 5 seconds later he's right back at it. It's killing me! What do I do?