How many people do you need to answer this for you Larry?? I agreed with the person that said you are wrong if you DONT put the dog to sleep. Your dog lived a really long time. You obviously took real good care of your dog. Do what YOUR heart tells you to do. I have 5 dogs.... I would find it very hard to put any of them down.
You are by no means wrong for putting your dog down. It is probably going through a lot of pain. I suggest making your dog comfortable in a quiet place in the backyard, calling the vet, and having him put down. It's like in Of Mice And Men, you'll be happy you did the right thing for your dog.
I have a family friend thats dog is in the same situation. She's not suffering so the doctor gave them something to help with the bathroom situation. But take your dog to the doctor and see if he's suffering and see what the vet says. They'll know best.
Only put him to sleep if you think it is a serious problem. It is your dog so it is your choice. My best friend had a dog that was 18 w/ the same problem . My best friend also has a 6 year old dog that hasn't walked on his own since he was 3. He still goes to the bathroom on his puppy training pads. They have to hold him up to give him water and food. He has to sit on the couch every second of every day. That dog has made it far and yours can too.