I have read your problem. I thing it is because of poor oral hygiene
. Ideal oral hygiene rule is to do brushing twice a day (morning and night) ,use antiseptic mouthwash once a day and clean your tongue with tongue cleaner twice a day when you are brushing. So think over it how frequently you are following this rule. Donot think about bad diseases , Start b-complex for one month along with good antiseptic mouth wash.
ALL the best.