Hi IWR,
Yeah, you'll need to practice and retrain yourself to breath properly. Lay down and breath like you normally would. If your chest rises, you need to concentrate on making your lower abdominal area expand. This is 'belly breathing' and the proper way to give your body a slow, steady supply of oxygen.
As far as the disbelief that anxiety is the culprit for all of your symptoms...Many people struggle with this, and I think that's why we spend so much time, money and energy going to doctors, and getting tons of tests. It IS hard to believe!
But you've got to make a choice to trust your dr. I had convinced myself at one time that I had a heart problem. I went in for a check-up and ekg. All was clear, and I asked the doctor how it was that I still felt so wierd. He said that the only other test he could do would be an echocardiogram, but that he was sure that it would also turn out normal.
I had to make the conscious choice to believe him. I didn't want to...I wanted the test, but I declined. That was a major turning point in my recovery. Taking a leap of faith, trusting that I was allright. I then sought therapy for my health anxiety.
Which brings me to my next point... ah you knew it was coming! Have you looked into therapy? It is highly effective in treating health anxiety. I went from debilitated to confident. It really works. And it can be used in combination with medication, or by itself. That choice is up to you:)
I hope that this helps in some way. Take care, keep posting, and let us know how you're doing soon.
Scaredy Cat