As you have mentioned, bad stomach and rotting teeth (decay and cavities
!) are the primary causes of bad breath
from the mouth. If you have tried all means and the problem still persists, it's high time to get yourself examined by a professional dentist
. That should take care of all your problems before it's too late. The decayed teeth can be filled and the bad stomach can be treated (by a Physician of course!). All the best.