Mysterious shortness of breath: What has helped you?

I will try to make this as short as possible, but this has been going on for over 5 years, so it might be farily long. 

Beginning in summer of 2012, I began having shortness of breath (SOB) with no other symptoms. I felt a constant need to yawn, and every few breaths wouldn't satisfy the SOB. I would take a deep breath, and felt like it would get "stuck" before satisfying the air hunger feeling. About every 3-5 deep breaths would satisfy it, only for it to return a minute later. 

I got an endoscopy and other tests done, which revealed that I had some esophageal erosion due to acid reflux and a slight hiatal hernia and was diagnosed with GERD. I had always have bad heartburn, so I was prescribed with Prilosec, which I have been taking daily since them. I've tried stopping it a few times but the reflux always comes back a lot worse. 

Lung tests and x-rays were normal. Heart tests normal. Blood test revealed a slight anemia but otherwise pretty normal. 

I did some research reading forums where someone suggested taking vitamin B-12. Strangely, I took it and the SOB disappeared almost instantly. However, it only lasted a few days for it to return just as bad. I then started taking an iron supplement, which again made the SOB disappear quickly- same thing; symptom returned days later. 

After further research, I came across a breathing exercise method called the Buteyko method. Essentially you do a lot of breath holding to build up CO2 and reduce breathing as the theory is that I had chronic hyperventilation causing too much CO2 to exit my body. After applying the method and reducing my breathing, the SOB disappeared after only 2 days and I felt completely normal. I continued the method a few more days then no longer felt the need to pursue the exercises. I was normal for a whole year when the SOB once again returned with some chest tightness. I applied the method again and the symptom went away, this time with a little more effort; after about 3 weeks. I included physical exercise which also helped with my breathing. 

After that, I was normal for about 2 years. I mistakenly stopped or at least slowed down exercise and the SOB returned once again. I applied the method and began running for exercise but the SOB kept getting worse. It got so bad, I had multiple panic attacks and the feeling of completely empty lungs with the inability to satisfy it with deep breaths. I had to stop exercise altogether, apply the Buteyko method and do breathing exercises very carefully with very light and slow exercise. This helped, but it took many weeks for the SOB to improve. Then, it was almost normal when over a year ago as I was running, I couldn't get a deep breath to satisfy exercise-induced SOB. I have had SOB continuously since then (a year and a half). 

I once again started doing breathing exercises and slowly building up physical exercise, but I can't do any prolonged cardio activity because the SOB gets to a point where deep breathing will not satisfy it. While the breathing exercises have helped, they have had very little effect compared to previous efforts. It seems that every time the symptom returned, greater effort yields few results.

I suspect there is something, some underlying cause that is causing the SOB that has alluded me this entire time. 

So for the past few months to a year, the SOB is worse on some days, better on others, but never gone. There's no rhyme or reason or pattern for it. It's just there, sometimes affecting my sleep. I sometimes can't get a deep breath to satisfy it every now and then, but for the most part, a big gulp of air will satisfy it. But it returns seconds to minutes later. It's as though every breath doesn't deliver what it's supposed to, the SOB builds up, and then I have to take a big gulp of air to get rid of the feeling, pattern repeats. My breathing pattern is normal, however. I don't feel like anything physical is happening, but sometimes it feels like my airways and nostrils are slightly inflamed due to allergies, but when I don't feel inflammation the SOB is still there. 

Recent lung function tests show normal- I don't have asthma, or any other problems with my lungs. Heart tests are normal though I did have about a two week bout of heart palpitations which came and went. Haven't had any for a while- it just mysteriously started happening then stopped. Blood tests are normal, though tests always show a slight elevation of biliruben which my doc thinks is Gilbert's disease. 

I don't have sleep apnea (normal test), bloody oxygenation is normal, heart rate normal. 

I recently saw local naturopath (since mainstream docs aren't able to help) who immediately suspected a liver problem when I described my SOB, possibly liver inflammation. He used an electrodermal testing machine to test his theory which did seem to show a problem with my liver and gallbladder. He gave me digestive enzymes and a gallbladder formula to help clear a bile duct clog, thus reducing liver inflammation. He also determined with the machine that I have an egg sensitivity so I've been avoiding eggs. 

Been taking this and avoiding eggs for a couple of months, but there has been no noticeable improvement. Everything else is normal. Emotionally I'm normal- no anxiety, depression, etc. The SOB seems to be the only symptom of something, but always comes back worse, until a year and half ago when it came back and has remained since. I feel like I shouldn't have to do breath holding exercises every day just to maintain my breathing well enough to do every day things. 

Does anyone have any idea of a possible underlying cause?

2021/2022 UPDATE:
Since my original post about 3-1/2 years ago, a lot has happened, so I’d like to update the post to share with others who come across this what I’ve done since then.

I have maintained a weekly Buteyko method breathing exercise regimen where I do a few of these breathing exercises 3-4 times a week in the morning. This, in combination with daily light to moderate exercise (specifically weight lifting, with 1 or 2 days a week of walking and light jogging), I feel has kept the air hunger symptoms tolerable and manageable. I have mostly good days with some not-so-good days, but doing a breathing exercise and knowing that it’ll get better again helps me get through those times.

I also have sinus inflammation which can exacerbate the symptoms, but I’ve also managed this, which in turn reduces the severity of the air hunger symptoms.

So, while I haven’t found a cure nor is the problem completely gone, I have been able to maintain normalcy in daily life and manage the symptoms through the strategies I described.

This discussion remains active, alive and well through the comments section where others who have similar symptoms have shared what has helped them as well as suggestions for possible solutions to explore.