Brief answer: Burning Mouth Syndrome.. Hi..Can understand your concern.. As per your complain it seems that you have a Syndrome known as Burning Mouth Syndrome in which there is burning sensation of mucous membranes of mouth which is commonly due to dryness of mouth and the bad taste in mouth along with other features like coated tongue and difficulty in eating are all due to dry mouth.. Dry mouth can be due to a number of reasons like Nutritional deficiency, Nerve injury that supplies the salivary glands , damage to salivary glands,salivary gland duct blockage,hypothyroidism,Autoimmune disease like Sjogrens syndrome,Thrush etc. The dry mouth leads to atrophy of the mucosa causing crustation and burning, decay in teeth due to insufficient flushing by saliva,bad taste as the taste buds need saliva for proper functioning,gritty feeling in mouth etc.. In this condition the mouth become more prone to infections like thrush.. I would suggest you to consult an Oral Pathologist and get evaluated and get proper investigations done.. For dry mouth you can use saliva substitutes containing methyl cellulose which can be instilled in mouth for lubrication.. Saliva stimulants like Sour candies and sugar free chewing gums can help by stimulating saliva flow.. Pilocarpine drug is also given as it stimulates the glands to produce more saliva.. Drink plenty of cold water to relieve burning and maintenance of dry mouth.. Sucking ice pops can help.. Saline gargles can be relieving.. Avoid hot and spicy food. Maintain a good oral hygeine.. In case if the tongue has a white cheesy coating then there must be oral thrush which is a fungal infection and it can be corrected by antifungal oral medicines like Fluconazole,Itraconazole and nystatin mouth washes.. Hope this information helps.. If you find the answer helpful kindly write a positive review and click on found this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora..