Pauline:
My heart goes out to you. I used to own a gorgeous GSP who I loved dearly. On a routine visit to the vet he was diagnosed with congenital heart disease. We were told that with medication he'd live for 6 months. How we cherished those few short months with him - & how much his health improved. Unfortunately - virtually 6 months to his diagnosis date - he wasn't in a good state. I sat beside him as he lay on his beanbag & was with him as he drew his last breath. It was a peaceful moment & even though it broke my heart to say goodbye (I didn't have enough time with him!!) I knew that I'd provided him with a happy life. That was 9 years ago. I think of him often & yes, I do still cry.
My condolences to you & your family Pauline.
There are so many great poems out there that may help you in this awful period & you may also want to try a site called Faithful Friends..I've found it very comforting.
http://www.faithfulfriends.com.au/
Best wishes