Popping in stomach/diaphragm area when leaning back?

[Pubgas687]

I have been getting this weird popping sensation in the area of my diaphragm whenever I lean back or puff out my chest (not painful, though sometimes itll hurt until I pop it.) I have been bloated for about 2-3 years and doctors always direct it towards IBS or ulcers (which I have both, including gallstones if it helps.) does anybody else have this problem? If so could somebody tell me what it is since apparently no doctors can figure it out?