See a dentist. In the majority of cases, the cause of bad breath (nose and throat/mouth), or halitosis, is the product of bacteria in the mouth and gum disease. The proper diagnosis is the key to a successful treatment. See your dentist for Halimeter test, diagnosis and bad breath treatment that depends on its cause. Good luck.
Determine the cause. Then start care. Your halitosis may be coming from periodontal problems, cavities, infections, or acid reflux. Once the cause is determined then treatment can be instituted.
Dental exam first. to rule out infections of teeth or gums. PCP or ENT to rule out problems with tonsils or sinuses, PCP or gastroenterologist to rule out stomach issues, PCP or pulmonologist to rule out problems with lings. Nutritionist and functional medicine doctor for proper diet and nutrition, stay well hydrated, consider oral probiotics such as Evora.