For about a month now, I've had what seems to be an air pocket in my stomach. I often have to let out gas (fart, sorry) and when I'm doing so, a lump the size of a baseball expands in my stomach to where I can actually see it. If I press on it before farting, it makes a very loud gurgling sound and then I fart (sorry for being graphic). I have to say, I did have gastric bypass surgery 10 years ago, not sure if that has anything to do with it.