See if you can find a new vet. Those sorts of symptoms, especially in an older dog, need to be checked out. Is your dog losing weight?
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."