Hi. Thanks for your query. Noted the history and understood your concerns. Constant burning in the upper abdomen above belly button along with headache, nausea and sore throat is indicative of stomach flu unless proved otherwise. I would advise you the following in such a situation. Consult your Doctor to get the clinical evaluation, examination and get started on symptomatic treatment with a PPI or Ranitidine, antacid, Domperidone. Get the investigations of blood, urine and stool. Ultrasonography of the abdomen is a must as also upper GI endoscopy if there is no relief. If required a CT scan in suspected cases of pancreatitis is a must.