Pain under the chest after eating is commonly caused by acid reflux, indigestion, or gallbladder issues. For immediate relief from suspected reflux, you can try an over-the-counter antacid (like Mylanta or Tums) or an H2 blocker (like Famotidine). However, because chest pain can sometimes indicate a more serious cardiovascular or gallbladder condition, you should be evaluated by a doctor. Avoid lying down immediately after eating. Please seek emergency medical care immediately if the pain is severe, radiates to your arm, neck, or jaw, or is accompanied by shortness of breath, sweating, or dizziness.