Re: bloating (and breathing difficulty) relieved by external pressure...
Probably need a little more information. How long have you had this? Is it a life long thing? How old are you?
The reason I ask is that I have had this my whole life. Especially in my earlier years,, up to 30. If you eat something rich in carbohydrate you feel like if you take in a deep breath (of which your body is craving to do so) that you may have a heart attack.
It's rather detailed what causes this, but bloating can occur from undigested food which does't break down in your gut. A quick solution to see if this is the case is to use some 'digestive enzymes' when you eat. For me, who is super sensitive to food, digestive enzymes work very well. Get something broad spectrum.
The other issue is that if you have had this for a long time, allot of this undigested food gets down into your intestines and if gone on for long enough can cause 'Leaky Gut Syndrome' where the tight junctions in your gut start to loosen and you get undigested food and byproducts of their fermentation process into your bloodstream. This causes an immune response and the immune response leads to idiopathic (temporary or as the problem happens) stress on our system. From what I understand it can cause idiopathic insulin resistance but the important point here is that it puts stress on our body and leads you to release too much cortisol (stress hormone). Stress hormones cause a contraction of blood channels (where blood carries oxygen) and leads to that shortness of breath feeling (tight chest). I've had it my whole life and have just learned to control it.
This means, no sugar or simply carbohydrates. I really makes a difference when you cut them out. Because our body has probably been like this for some time (well I'm assuming), then eat protein with meals to keep your blood sugar even. Until your stress levels calm down, you will need to do this.
Hope this helps. It's general but I can tell you , it's almost certainly what you have.