Since how long is the pain?
How severe is the pain on the scale of 0-10?
Do you have; nausea/vomiting, heartburn, sweating, breathlessness, pain radiation to arm, bloating, gas, constipation/diarrhea?
Any significant past medical illness or surgery?
off and on for 3 weeks
acid reflux, fibroneuralgia although i due suffer from constipation often i do not think that this is the problem at the moment
Following are the possibilites for this pain;
1) Hiatal hernia
2) Peptic ulcer
3) Gall bladder stone
4) Esophagitis (food pipe inflammation)
You would need an upper gastrointestinal endoscopy and ultrasound for the diagnosis. A test for Helicobacter pylori too would be important and if it comes out to be positive, will need triple antibiotic regime for it's eradication. If you have any risk factors for heart (obese, high blood pressure, diabetes, family history, high cholesterol etc), it is mandatory to get an EKG for upper abdominal pain of this severity to categorically rule out any heart association (which can be a concomitant problem with the abdominal disease).
Please feel free for your follow up questions.