I had this for about a month and it is finally going away after an Upper GI scope that I had three days ago. The doc found nothing. Not even Acid Reflux. It was that same gnawing pain and pressure. It radiated up to my collarbones and to the middle of my back, even causing some breathing problems. It even hurt my sternum to wear a bra. I originally thought I was having a heart attack--went to the ER and came out with a perfect cardiogram. HOWEVER, in my case, I know that it is alll caused by ANXIETY. As soon as it started going away, I started getting some nuerological feelings in my head (which I've had before). Also anxiety. I've had every test I possibly could and need to face that fact that about 95% of the health symptoms I experience are ANXIETY rearing it's ugly head, and as soon as one worried-over symptom starts to go away a new one arrives.
I think what happens is there might be a mild discomfort, or strange feeling somewhere...minor aches and pains that EVERYONE gets. But, because we are anxious-natured, we say, "What if it's _____________?" and we fixate on the area and that just makes us more aware of every little nuance of what we are feeling, basically turning a tiny zit into a festering boil, so to speak.