One possibility is that a part of your bowel routinely allows the buildup of gas which causes the pain behind the ribcage, especially during a deep breath. Because this has been happening to you for so long, and because medical professionals have not been able to help you, you are probably beginning to have anxiety attacks whenever you experience this pain.
The tightening of the throat, is a classic anxiety symptom. It, plus the pain when you breathe deep, causes you to take rapid shallow breaths leading to slight hyperventilation which causes the dissyness. At this point you begin to pass from anxiety into a panic attack which then leads to the nausea.
When I read your post I recognized what I went through a while back. Fortunately I had a doctor that inadvertently told me what the pain under the rib cage was when I had an x-ray, totally unrelated to the pain, to look at my lungs regarding pneumonia. As he showed me what I was looking at he pointed at what turned out to be gas building up and asked me if I ever had pain just behind my ribcage when I took a deep breath. Voila!! My mystery was solved!
Please consider getting some symethicone at the store. Symethicone breaks up big bubbles of gas into small bubbles of gas. It's sold as Gas-X or Phazyme but it's all the same so just get the most economical (usually store brand) package. It doesn't matter if it's gelcap or tablet, but I actually buy both. When I feel the gas building up I swallow 1 or 2 gelcaps and then chew 2 tablets. The tablets work in my upper 'gastro' tract while the gelcaps seem to help with the lower end. The result may be a few burps and a short spell of 'pooters', but that's how you get the gas out.
I am not a doctor. My answer to you fits all of my own symptoms, and the anxiety and panic attacks I had had were eventually explained to me during psycological counselling. Best of luck to you!!
