I am sorry you are going through all this. I can tell you what I did and maybe will ring true for you. I have GERD, hiatal hernia, and laryngopharyngeal reflux. I suffer chest pains and coughs and belching. I was on a PPI (omeprazole) for four years without blood test monitoring and discovered by chance that I had developed chronic kidney disease, stage 3. I weaned off the PPI and my CKD improved; it was an acute kidney injury caught in time so I improved into the reference range. I will say the PPI managed my symptoms so I could eat almost normally.

You said you tried diet, etc., but let me tell you what I did in that regard.

I bought Dr. Jonathan Aviv's book on low-acid, whole food diet, and joined the FB page that has a ton of recipes based on his diet (acid watcher warriors I think it's called). I also went to the web site of another ENT, Dr. Jamie Koufman, which has a lot of good free advice. She also has a book on a low-acid diet. I followed a lot of her advice, e.g., the diet, alkaline water (be careful if you have filtered water. Check to see if it's acidic. If it is add alkaline drops); Gaviscon Advance from UK, chewing sugarless gum, sleeping on an incline (actually I sleep sitting up), spritzing my throat with alkaline water. When I follow the low acid, whole food diet I feel better, no chest pains, less belching, no reflux. It is difficult, but when I eat highly processed food or acidic foods I feel worse. It took more than a month for the worst symptoms to start abating.

My GI doc wanted me on PPIs or undergo surgery. I opted to try the diet/lifestyle protocol because it had less chance of side effects. If diet/lifestyle changes don't work for you then I suppose you need to do more testing to see if there is something else going on besides plain vanilla GERD. Good luck!