I do sympathise, heartburn is horrible.
I had it intermittently for years - often linked to stress - and I was hopeful that low carb would cure it , as all posts indicated it would !
however, I found no difference during my first few weeks low carb , maybe even worse. Water made it 100 times worse ! then I was advised to add more fat to my diet. Having been low fat for many years ( while steadily gaining weight I might add !!) Instant cure. I now have to really think about it to add the fats, but it works a treat. the only thing nowadays to set me off is decaff. coffee. one small cup I can tolerate.If I have too much, one teaspoon of olive oil cures it.
Adding extra olive oil, and mock Danish for breakfast have really helped.. best of luck....