My mum was plagued with that problem all her life funny thing is she found Psyllium husk solved the problem. It's a soluable fibre and acts as a laxative (it's in Metamucil). She buys the fibre in bulk rather than Metamucil. She was using that when she noticed the stomach problem disappeared.
You should see it soak up liquid 
Last time I saw her she sprinkled it on her salad. It goes soft as soon as it picks up moisture. Lot more natural than drugs and my mum prefers it.
Alex
