Bad breath can be due to bad condition of the gums, decayed teeth or from bacteria colonizing at the back of the tongue or sometimes it can be due to certain systemic illness.
Visiting the Dentist and getting your teeth cleaned, filling or extraction of decayed teeth, etc. shall take care of your bad breath. Certain mouthwash such Chlorhexidine prescribed as an adjunct to the appropriate treatment will also help eliminating the bad breath.