This is a very interesting and well set out question. Left-sided chest pain is not uncommon in teenagers and young adults. First off this pain is not due to your heart. It is called internal mammary artery pain or the Da Costa Syndrome(Google 'Da Costa syndrome') The pain itself is due to spasm of the internal mammary artery which is found on the inside of the chest wall. The cause of this spasm is usually due to stress. This is not a dangerous condition and you will grow out of it, When the pain occurs just relax and take a few deep breaths. If the pain worsens or becomes persistent you should see a doctor about it.
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