I'm so sorry he is such a sweetie, i sincerely hope that he stays with you for as long as possible and is comfortabl and not in pain.I hate to say this, but if you think at any time that he's in pain, he really has to go to the vet. The chances are that they will put him to sleep, but there may be something that they can do. Otherwise, it is better for him to pass on peacefully and in a dignified manner rather than suffering. It's so hard, and i feel for you. But i really hope that it doesn't come to that. Keep going little Domino.