We had a GSD when I was growing up that did the same thing. It started when she was about 13 years old. She lost all control over her bowels - but if she saw that she had pooped, she was always so embarrassed. I tried to clean it up before she would see it because I knew she couldn't help it. Soon after that, she totally lost the use of her back legs. She lived with her back end paralyzed til she was 16 when my mom finally let her go to the bridge. (RIP Bunny).
Livin in a Newfie Drool Zone