Might be that the stabilizing muscles are weak or just not as strong as rest, the plank really helps. Or it just might be that the only real solution is cosmetic surgery (it's rare that it's the only option) but some guys have to through it to get to the level they want.
Op,It is nothing else but indigestion. Guaranteed. You're holding food/liquid in your stomach for an excessive amount of time rather than it being digested and assimilated quickly as it should. Start taking digestive enzymes with every meal and probiotics in between and I bet it will go away.And to the stupid fucker above, if he ate nothing the bloat would go away, so quit with the useless bullshit comments "eat only fish/fish and rice". You expect him to stay on that diet forever?
If you squat, and deadlift, your stomach/torso can get quite muscular. I don't know if it is as bad as you think, it's ok if you have a muscular belly.