Are the symptoms consistent or paroxysmal? Are they related to physical exercise? Will a deep breath worsen it? How old are you? Have you ever been diagnosed with digestive ulcer?
I think it might be related to ischemic heart disease, pulmonary embolism, pneumothorax, aortic dissection, pneumonia, stomach cancer, intercostal neuritis, pleurisy, esophagitis, hiatal hernia, esophageal cancer or lung cancer. You should go to the hospital.