OMG this sounds sooo much like my dalmatian, Molly, who has passed on. She started to lose control of her bowels at about 9. She seemed to not know that she was having a bowel movement. She would also walk along and poop, but not even be aware of it and then she started to lose control while she slept (on the couch). It seemed like she would relax so much that it just slipped out. Gross, I know!!! The vet never really figured out her problem and we just lived with it and constantly checked her and did loads of laundry (couch covers). The day she passed away, I dragged the couch out to the garbage.
I have no advice other than to see a vet but I do know what you're going through.