Oh my, that is so sad! Could it possibly be arthritus? It can happen to even younger dogs. If so, I know of a wonderful drug called arthromine (spelling?) Ask your vet about it, it can also be found cheaper on internet sites. My dog is 16 and wasn't able to hold himself up and he limped/whined. After 1 month on that stuff he was like a puppy again. Maybe you should check it out. I pray that you find a way to relieve his pain. All you can help him with for certain is supply him with endless love and affection.