This could be an ulcer or your gallbladder. The best thing to do is see your doctor.
You might be dealing with a case of mild gastritis. (5-6 cups of coffee is a lot.)
For the moment, eliminate all caffeine, all coffee (decaf included), all carbonated beverages, all spicy foods, and all citrus. (In short, keep a GERD diet.) Keep it light for a few days. Get some aloe vera extract to drink and chewable DGL tablets (you can get these at your local health store). Take these as per the instructions for at least a week. Drinking chamomile tea is also good. You may also want to add an OTC antacid like Pepcid or Zantac (an H2 inhibitor) for the moment.
If you follow this for a week and don't start feeling better, go see a doc.
If you do feel better, keep on the antacids for another week then knock them off. Continue on the DGL and aloe for at least a month, then try slowly to reintroduce the foods you eliminated. If after the antacids the feeling returns, go see a doc.
Good luck.