Abdominal pain and constant burping can result from medical conditions, some of which are also accompanied by gas. The pain and burping also can be caused by naturally occurring gases within the stomach and intestines.
Abdominal pain and constant burping are possible symptoms of gastric cancer. Ask your doctor about this before considering other causes.
Ulcers and Hernias
Pain and burping also can be caused by peptic ulcer; intestinal or hiatus hernia; or Helicobacter pylori (H. pylori) bacteria, a common cause of stomach ulcers.
Other possible causes of abdominal pain and constant burping are indigestion, which creates a general feeling of gastric discomfort, and gastro-oseophageal reflux disease---also known as acid reflux or GERD---which occurs when liquids from the stomach back up, or regurgitate, into your oesophagus.
If you eat too fast, smoke or chew gum, you may take in large amounts of air, causing gas that results in burping. Gas also can result from the normal breakdown of undigested foods.
Hold the Onions
Remember that gas alone can sometimes cause abdominal pain and constant burping---as anyone who has eaten a hot dog with onions can attest.