From your description of the pains, as well as the negative findings of the ER studies, it seems very unlikely you're having heart-related symptoms. Pain below the left breast, into the armpit and otherwise as you describe are rarely heart-related, and in fact may be due to GI or orthopedic (usually rib cartilage) problems. The right-sided pains you describe don't fit the profile of heart pains even remotely, as they are sharp and traveling in the wrong direction.
The fact that the inflation of the blood pressure cuff triggered pain retrograde to toward the usual area of origin suggests a possible nerve compression problem.
Lacking risk factors and having had a good result in the workup in the ER, plus the highly atypical (for cardiac purposes) pains, I strongly suspect no heart involvement, but possible orthopedic/nerve-related pains. You might want to pursue this angle if the pains become excessively bothersome.
Best of luck to you. Please follow up with us here as needed.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist