Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain bitter taste after eating. nausea. pain in lower back, right hand side. lethargic. lose of weight. yellow coating back of tongue. often burp and flem in back of throat in mornings Well, all these symptoms are indicative of acid reflux and it leads to regurgitation of acid and food particles from stomach to food pipe and throat.. It leads to excess mucous formation and also coughing.. Yellow coating on the back of tongue seems to be due to accumulation of the food particles on the back of tongue due to reflux of food particles and acid.. I would suggest you to consult a Gastroenterologist and get evaluated and a thorough clinical evaluation and investigations like upper G.I Endoscopy can help in diagnosis and treatment can be done accordingly.. You can be advised to take Proton Pump Inhibitors like Omeprazole or Pantoprazole.. Take antacids like Milk of magnesia.. Avoid spicy food and drink plenty of water.. Always take walk after meals and take your dinner atleast 2 hours before sleep.. You should sleep with head slightly raised as compared to feet.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.