Where is this problem? It doesn't sound like a simple stomach problem.....but it could be lots of things. Do you have a fever or have you had one recently? This would indicate an infection of some sort. Infections are not always accompanied by fever, but usually they are.

It almost sounds like a kidney infection or maybe a UTI. If it is on the lower right, then that would be appendicitis.

The only way to find out for sure is to see your doctor, and I think you should right away before it gets worse.