Hi in regard to your query, you have mentioned that you had visited doctors and dentists but you have not mention what did they say.Basically bad odour from mouth is of many reasons either coz of poor oral hygiene or any systemic diseases like diabetes, liver insufficiency, kidney diseases etc... since you have mentioned something like dead i would suggest you check your diabetic status since you are healthy with your gastric status.I would suggest you to undergo complete health check up with your systemic status and make sure you are healthy and go for dental check upp to confirm that your oral health is good tooo. Hope this is helpful.Without treating the systemic cause treating the only oral causes will not help.Hope this is helpful.