Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain metallic or tinny taste in mouth along with chest discomfort especially on reclining seems to be most probably due to Gastro-esophageal reflux disease commonly known as Acid Reflux in which acid from stomach refluxes into food pipe and throat and due is more on lying down due to posture which eases the flow of acid upwards.. Consult a Gastroenterologist and get evaluated and he can advise you upper G.I Endoscopy for confirmation of diagnosis.. You can be advised to take Proton pump inhibitors like Omeprazole or Pantoprazole and H2 blockers like Zantac[ranitidine]. Take antacid like Milk of magnesia or Calcium carbonate. Drink plenty of water, avoid spicy,acidic and large meals.. Take frequent small meals like eating every 2 hours. Take short walk after meals and finish your dinner atleast 2 hours before sleeping.. If you are obese loose some weight.. While sleeping you should keep your head and chest portion slightly raised as compared to feet to reduce the acid from coming up.. If you sleep laterally prefer left lateral position.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.