Need advice on what is the the cause of bad breath?

Many reasons. Bad breath can be attributed to many causes medications tooth decay gum disease stomach problems if food products stay in your mouth and decompose they will cause bad breath have it checked out if you have bad breath.
Many causes. There are many reasons for bad breath, both dental and medical. The vast majority of times it is caused by poor oral hygiene and periodontal (gum) problems. See the following website for more information: http://smilesapartcosmeticdentist. Com/fresh-breath-control. Htm start with a dental evaluation.
Many causes. Many things can cause bad breath, including cavities in your teeth, periodontal problems, acid reflux, sinus infections, and diet. Since you cannot be evaluated for all of these conditions over the internet, seek the care of a local dentist and physician who can examine you and treat you.