I was heartbroken reading your post. I do know how you feel though. This past July I had to put to sleep my 12yr Malamute cross and it was the hardest thing to do! No one else in my family had the courage to come but a good friend came with me. The hardest part was because he didn't really act sick. He had a basketball size tumour on his side and was losing weight like crazy, vomiting everytime he ate. He would run around and play like nothing was wrong then when he went to lay down he would whine in pain. It was heartbreaking. I cried all the way to the vet and all the way home but I know in my heart it was best for him. I still miss him everyday. Good luck and remember he will thank you when he is looking down from doggy heaven
