Dear Robbie, as the others have said it is time to let him go, we had to make the same choice with our Chocolate Lab, he had bowel cancer, had 3 operations in the hope of prolonging his life, we went for a check up from the last one, the news was bad, it was spreading too fast, I am sure he knew what the vet was saying, he looked at us with such pleading in his eyes "let me go Mum please" I knew then the time was exactly right.
You will know too if you look into his eyes, will be thinking of you