It sounds like your symptoms are from your GI tract and you might have aerophagia--swallowing air. You might need to have an upper GI endoscopy.
To elaborate a little on this. I have never experienced indigestion before this. I am 5 ft. 4, 148 lbs. My usual weight was always around 135 to 140, however I had a baby (my fourth) 9 months ago and have not lost all the weight yet. I am a smoker, a pack or pack 1/2 a day. When the belching began I had mild pain in my upper abdomen, right in the middle under the breast bone - that has subsided. Now my only symptoms are the belching and anxiety.