If you're doubled over with tummy pain and you haven't thrown up and gotten rid of it, get to an emergency room, pronto! It could be poison, a blockage of some kind, your intestines could be dying from an injury (happened to my dad -- he almost died!), could be colon cancer that has developed to a late stage, and on and on. Don't play around. If something is really wrong, you know it.
Stomach ache can occur from various causes. It could be a slight disorder or a serious illness. Find out where the pain is coming from, whether lower or upper abdomen. Contact a doctor for professional advice. Check out http://en.wikipedia.org/wiki/Abdominal_pain.