Have you tried an elimination diet to check whether it could be a reaction to something you're consuming?
- Claritin
- Flonase
- Ranitidine (Zantac)
- Omeprazole
- A diet based around avoiding things that "might" cause heartburn. This list included literally everything I eat; this project had to be abandoned. But for a while there I was basically only eating chicken soup and milk.
- An allergy battery (negative on all tests)
- Nasal irrigation
- Mucinex
I had the same issue, and it didn't respond to Inexium (PPI) but cleared up totally with Pantoprazole.
The ranitidine, omeprazole, and pantoprazole are all intended to treat pain[1] from heartburn, and they've all worked at first and gradually lost effectiveness. (While still being mostly effective, just not totally effective.)
However, going without heartburn pain for weeks at a time has not helped my throat. When this didn't work, the gastroenterologist put a sensor down my throat for a day to record pH levels, and reported the results to me with "good news! You don't have heartburn!"
Of course, I do have heartburn. The response to "in that case, what does it mean that I have this burning chest pain after eating which is immediately relieved by tums?" was "well, some people are more sensitive to acid than others".
(I have many classic symptoms of acid reflux, including minor regurgitation of food after eating, "globus sensation" (feeling of a ball in the throat) when swallowing, and of course burning pain in the chest.)
But I continue the heartburn medication anyway, because heartburn hurts and I independently want to avoid it. :/
[1] Actually, they're intended to suppress the acid itself, not the pain you feel from exposure to it.
The theory is: instead of "too much stomach acid" being the problem, sometimes it's "too little stomach acid". Age, medications, and infections may all lead to reduced stomach acid production, which leads to unwanted fermentation and impaired digestion of carbohydrates in the stomach, which increases the production of gas, which increases intra-abdominal pressure, which causes the lower esophageal sphincter to malfunction and let the little acid that is left travel up into the esophagus, where it irritates the lining and can cause symptoms like you describe.
Might be worth looking into. A simple way to test this theory would be to get a "Betaine HCL with Pepsin" supplement and take it with meals to see if that helps. Do not try this if you have ulcers or other issues with the integrity of your stomach lining.
I only mention it because this approach cured my persistent heartburn and sore throat issues, after various PPIs worked for a bit and then failed. Conventional medicine is great, but why they continue to recommend PPIs for chronic GERD cases is a mystery to me. The stomach is meant to be acidic - the goal should not be to neutralize the acid.
Good luck!