See your dentist. See your dentist. Have the dentist rule out decay and periodontal disease. Have enhanced hygiene-- brushing at a forty five degree angle between the tooth and the gingiva, flossing correctly, using a tongue scraper and possibly a prescribed rinse. If the etiology is not determined to be dental, a MD consult may be needed.
See a dentist. If your teeth are not the source of this (often due to disease of the gums), a search for the source (sinus infection, esophageal diverticulus, tonsillar disease and other conditions may cause this. Cannot suggest corrective measures until you know what is responsible.