Bad breath is caused due to-deposition of plaque or food debris.
This can lead to gingivitis
I would suggest you to visit a dentist
and get a thorough scaling done.
Use soft bristled toothbrush and clean your teeth involving all aspects of it.
mouthrinses to gargle.
Rinse your mouth after every meals.
Take plenty of fluids and nutritious diet.
Vitamin c,iron supplements
has to be administered.
Hope this helps.