This could be Heliocabacter. MY daughter had this from around the age of 8 and it got progressively worse. It was diagnosed via a poo test which our very good GP sorted. It turns out she had had it from birth, probably picked up in the hospital. Her stomach lining was severely inflamed and she was in a lot of pain when it struck, particularly when doing sport, when all the acids were moving about in her stomach.
We were referred to Dr Chong, as mentioned above, after standard antibiotics failed. It took an endoscopy, a couple of courses of strong antibiotics and then finally a breath test afterwards to show that it had cleared up. After diagnosis her diet had to change until her stomach had healed itself but she was back to eating everything soon enough.
Touch wood, it hasn't come back but it was very debilitating when she had it.