I think it's just severe IBS, with gas. I had this problem forever, and had always thought it was the worst case scenario (Colon Cancer, LGS/Leaky Guy Syndrome, Bowel Obstruction, Crohn's Disease, or a hole on my colon wall) when it's just really something really simple I'm sure. You should try swimming. See if you can submerge yourself into a pool without having a bloated feeling of being pushed up like a balloon (not for fun, but just as an experiment). It happened to me in 2004. It's definitely gas none the less, a shitty malodorous constant fart.
How's your deit? Are you eating normally, or healthy, or are you a fast food buff?