Thanks for asking the query,
Bad breath can be because of several reasons.
It can be because of poor oral hygiene , plague
and calculus deposition, periodontal infections, tongue coating , xerostomia
, faulty restoration retaining food and bacteria , oral pathologic conditions , mouthbreathing habit, use of certain medications, use of foods like onion , garlic and alcohol.
It can also be due to diseases of GIT ,GERD
, Pulmonary diseases, nasal infections , diabetes
I would advice you to get complete physical and oral examination done.
Go for complete mouth scaling and polishing done,
Maintain a good oral hygiene.
mouthwash gargles twice daily.
Hope this helps out.