There are several causes for this, depending on the dog's age, gender, neutered (?), history, breed, etc. The best way to determine what is causing the swollen belly, and determine the appropriate...
Ear infection, ear mites, or an injury. Any irritation to the ear causing the dog to shake it too frequently and often to hard..ear mites are common, and most often found in puppies and young adult...
No, rubbing a dog's belly does not cause depression. Too much change, not enough exercise, play, can cause depression in dogs. A great resource for information on dog depression is:...