I think Flaps Forty has the best suggestion so far MDL... Have some thorough checks before you start flying.
Even the most trivial conditions can be exascerbated by flying (e.g. Headache, toothache etc ...)
If you have heartburn and indigestion frequently, there can be a number of causes for this, and until you get it diagnosed, you may not be able to treat it effectively...
If you take it back to basic terms... When an aircraft becomes pressurised when reaching altitude, everything (you've seen what happens to a packet of crisps inflight?) is filled with pressurised air... That includes your stomach, (hence bloating). This may not be an issue during the flight, but when it comes to depressurising the cabin (or heaven forbid a decompression), all that pressurised air will vent out of your system (in all manner of ways!
) Thus unsettling your stomach contents etc. If there is for example a problem related to your 'gastric juices' , that niggling pain may become something a lot worse! ... As flaps forty said... Do you think you'd then be able to a door on hearing the command to evacuate when you're in that amount of pain?
I'm not trying to put a dampener on things for you at all, but please consider your own health first, and get it checked.
Remember in an aircraft you are also working with reduced oxygen levels... Your body is already working harder itself to keep functioning normally, add onto that physical and mental exertion, as well as the normal stressors of flying ...
You are your number one priority.... Take care or yourself first eh?
BoB