Hi, you may be suffering from gastritis, and peptic ulcer disease, the fact it improves with anti-acids and meals suggests a possible ulcer in your stomach. I suggest you see a gastroenterologist for further evaluation, if i were one I would do an upper endoscopy to check your stomach walls. Now maybe the antacids your taking cause constipation specially if compound of aluminum, I suggest using the ones with magnesium and even better taking omeprazol 20mg daily. Also, if possible consider many small meals daily to avoid fasting and pain. How is your body weight? and how long have you been feeling this way? Hope you do better and any further concern please consult us asap.