Hi Briony - I am not sure, it's such a personal thing as to what triggers it. I have suffered in the past with the top button scenario. I used to drink warm water, when I felt bloated and cramped, sip it slowly or peppermint tea is also good. I had to lie down sometimes and consciously relax what I could of my stomach, circular motions around my belly. Posture was an issue for me I think, so anything you can do to improve that and your spine alignment will help I think, gentle stretches............everything gets tense which doesn't help.
Do you know if particular foods are also not helping? If not, you could try adding more fibre. Do you have a juicer? That's a good way to do it, but can be a bit much for the stomach - oh gosh, I really feel for you, it's horrid. I think a good yoghurt with live cultures is definately worth doing - the probiotics in that will be gentle and it's easy to buy and try. eat that before you eat a meal, a little while before.
Hope you feel better soon x