Hi.. Thanks for the query.. I have gone through your query and can understand your concerns.. As per your complain white coating on Tongue with bad breath seems to be most probably due to fungal/yeast infection known as Oral Thrush. It can occur due to a number of causes like compromised immunity, dry mouth, diabetes, intake of antibiotics and steroids etc.. The coating will not go away with only scraping and you need to take proper antifungal medication.. You should consult an Oral Physician and get evaluated and if Thrush is confirmed as diagnosis the Physician can advise you to take antifungal medicines like Fluconazole or Itraconazole orally.. Nystatin mouthwash and clotrimazole lozenges can be advised.. Taking more of probiotics like Yoghurt and Garlic will help in faster clearing of fungus.. Drink plenty of water to prevent Dry mouth that is common in Thrush and chemotherapeutic agents intake.. Hope this information helps.. If you have further questions you can visit my profile and ask me your question for a detailed discussion.. Regards..