First of all,,start brushing twice daily after meals,,then get a scaling done from a dentist,the bad smell from mouth occurs due to accumulation of food.

Bad breath can be due to poor oral hygiene, presence of cavities or underlying heath conditions. You need to first visit the dentist to find out the cause of your bad breath for complete elimination of the problem. Use of chlorhexidine mouthwash for a period of 2 weeks can assist in overcoming bad breath. I suggest you visit a dentist or a Periodontist or you can start a practo consult for complete resolution of the problem.