Bad breath can be be due to ulcer , but the main reason can also be bad oral hygiene,. If there is plaque accumulation, it could be the biggest reason. Also if there is caries involved in any teeth, that can cause bad breath too.
You should first consult your dentist for any of the above reasons, and treat the underlying cause, and you can start using Hydent k tooth paste and mouthwash. But mouthwash again should be used after knowing what ulcer you have so ask about that to your doctor.
Next Steps
go for oral prophylactic first.