Have you been through testing for reflux and the like? I hope you're seeing a specialist for it, just taking pain killers is not a solution, just a temporary relief giver til you can find out what's wrong.
I'm just speculating here, but if you've already been tested for the obvious causes, then maybe there is something in your diet that you are reacting to? Food intolerances/allergies can often cause things like hives or rashes, even inflammation in areas - its worth looking into alongside your other medical explorations. My Aunt had problems with her skin for years, was just given the usual creams etc, she finally by chance stopped eating something and they miraculously disappeared - turns out her body was reacting to that food, just wasn't a full blown allergic reaction so harder to detect.
I have found ginger capsules help with internal inflammation, aloe vera is supposed to be good too and these can be taken alongside your other medication for an extra boost.
Sorry couldn't be more helpful.
GERD, Anxiety, Depression, Rolling Hiatus Hernia, Esophageal Hypersensitivity