Hi.. Can understand your concern.. As per your complain dry mouth along with white coating of tongue and burning in throat is indicative of yeast infection known as CANDIDIASIS or ORAL THRUSH.. It is characterized by formation of cheesy white patches over surface of tongue along with dryness and burning sensation in mouth and dryness of mouth can cause dryness extending to throat leading to irritation and burning.. Even the white patches or the infection can extend to the throat.. Lethargy and dizziness can also be due to infection.. I would suggest you to consult a dentist and get a clinical checkup done to rule out whether it is fungal infected or something else by doing a microscopic examination of the scrapping from the lesion.. In case it is there is thrush antifungal treatment with antifungal drugs like fluconazole and nystatin mouth washes can provide relief.. Adding probiotics to the diet like yoghart and garlic can be helpful.. Maintain a good hydration by drinking plenty of water.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora..