I'll try to make this as short as possible:
I'm a 28 year old male in decent physical condition. About 2 months ago, my heart started racing inexplicably. I panicked, thinking it was a heart attack, and went to ER. They checked- no heart attack. I did a cardio test and had an ultrasound- all good. So, things were fine. Then, about 2 weeks after all this, I noticed I was having trouble breathing from my 'upper' chest- the upper chest muscles felt tight. I used my inhaler (I have very mild asthma), which didn't help. I was still able to run, exercise, etc., so while I'm concerned about it, I don't think too much of it. I went to my allergist, who confirmed my peak flow was fun, lungs sounded good, and suggested (as did the cardiologist) that my problems could be entirely anxiety-related. This makes some sense to me, as I've worked long hours (and pulled 3-4 all nighters in the last few months, for the first time in my life). However, I want to make sure. My breathing still feels 'lower' in the stomach than normal, even when I don't feel anxious. Any ideas? Is this entirely stress?