Hi I have gone through your query; and personally suggest you that before any treatment first rule out the cause of your symptom. looking at your history stomach cancer is very unlikely you need not to worry The first possibility is of Peptic ulcer disease or Hiatal hernia. Diagnosis can be confirmed by upper GI endoscopy. Try raising the head of your bed about four inches with blocks. It also might help to avoid eating or drinking for two hours before you lie down. To help control the stomach acid, one should not drink alcohol or drinks with caffeine in them, or eat chocolate or spicy or greasy foods. Also take some antacid but if the symptoms are severe, then you may need drugs like proton pump inhibitors. The second possibility is of pancreatitis as it may cause upper left abdominal pain which is worse when bending over or sitting. Pancreatic enzymes like serum amylase and lipase should be measured to rule out any pancreatic cause. I suggest you to consult a physician and get an ultrasound upper left abdomen, pancreatic enzymes, upper GI endoscopy to rule out any peptic ulcers and a chest x-ray done. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions. Wishing you good health. Thanks