Sorry for your loss and what you're going through. I had a cat with cancer that went from happy, lively, and hyper, to downright decrepit, unhealthy, and hiding from me, over the course of a couple months. We had to put him down, and it was the only thing we could do, even after thousands of dollars in medical expenses he still wasn't happy, enjoying life, or able to really live on his own will anymore. His last days were spent healing from surgery, and hiding from his only friend (me), because I had to shove pills down his throat 3-5 times a day. It was the saddest thing I've ever had to do in my life, and it killed me, because I was his owner, his best friend, and I was also the one that had to make the choice to end his life. I honestly think about my cat Rambo almost everyday, and it's been 10 years now. I have new cats that I love dearly, but I'll never forget that whole ordeal. It's a crummy situation.

I know what you're going through. It sucks. Get a new dog, and give more animals a good life. It's the only and best thing you can do.