LPR (Laryngopharyngeal Reflux) Disproven - Still Having Symptoms

I've been suffering from what I believe is LPR reflux for 16 months now, and I honestly can't take another day of it. I've been through everything to try and cure it from day 1. This includes all sorts of PPIs/H2 blockers, Gaviscon Advance, 3 different diets, 3 different antidepressants, alkaline water, raising the bed, vitamin d3 (1000-5000 IU a day) and more besides. Nothing works at all, and I'm not a candidate for surgery. I've had all the tests which are expected to come back negative too; the endoscopy, barium swallow, gallbladder scan, ENT throat scope all came back clear. I also have no new allergies, and my vitamin D3 levels are high enough to satisfy even the "new" research. Personally, I think the whole D3 thing is a hoax, but I digress.

I've also have a number of "Peptest" spit tests throughout the year. In total I have collected 18 samples, and only a single one has come back positive. It was the first one I ever collected, and it was only just in the "low" bracket of pepsin detected. That's just 1 positive sample in 17 though, and I've collected samples right after serious symptoms, or even when I thought I burped up vomit. RD Biomed, the ones behind the test, are questioning my self-diagnosis of LPR, but still my symptoms continue. They include:

- Constant Post-Nasal Drip. It doesn't wake me up in the night but the moment I wake up it affects me all day.

- Throat clearing, usually a result of the above.

- A burning throat sensation. There's no pattern with food, it has even happened when I drink alkaline water.

- Sinus headaches, fatigue and ear pressure.

- Nausea and constant burping.

HOW CAN THIS NOT BE LPR?! I have serious anxiety about my health, and the thought of having LPR scares me to death, to the point I have sought assisted "self-harm" to end my suffering. I refuse to live a full life with a chronic, painful, incurable illness, because it's the one thing I've ever been afraid of having. I'm just not strong enough to cope with it. In my desperation, I keep trying to prove if stress can cause all my symptoms. It does not, cannot and will not ever be the cause. I've been told to "stop deluding myself into thinking I'll ever get better" by some people, and told it's "all in my head" by others. Nobody truly believes I'm suffering at all.

Who should I believe? Will I ever recover? What kind of conditions are similar to LPR? Please help me. I want my life back.

A last, important note. I recently stopped taking Mirtazapine after hearing they have anti-acid effects. I refuse to be on drugs for life; I want to cure my illness, not mask it. Since stopping the Mirtazapine my Post Nasal Drip has significantly worsened. I'm not sure if the two are linked, but I've made sure to take another set of Peptest samples to check for LPR, and they're still all negative.