What do you mean by bubbly stomach? Do you mean gas in the dog stomach? If yes, then what other symptoms your dog is showing? If your dog is showing signs if illnesses like restlessness, pacing, drooling, foamy vomiting, unproductive vomiting, laying down on belly, loss of appetite, lethargy, curling up in ball, red or white gums etc then he might be having canine bloat that is dangerous condition in which stomach become filled with air. After eating. This condition is diagnosed by blood tests and is medical emergency that requires vet visit immediately. If your dog is doing well then no need to be worried.