When you experience something tragic, (being dumped, losing a family member, missing Monday Night Football, etc.) why do you feel it in your chest? Why do you literally feel like you have a broken heart?
I really don’t know.
Another place that true emotional agony can be felt is in the abdomen. I have noticed that fear and dread produce quite powerfull feelings of pain in the abdomen as well.
I’ll be watching this thread with interest.
Forbin
Ask anyone who has ever had acid reflux. They call it “heartburn” for a reason. While I’m not clear on the exact anatomical details, I believe the nerve bundle from the stomach is shared with that from the heart region. So stomach pain can be registered as heart pain (and vice versa). Knowing this, the rest is pretty obvious. You undergo stress, your stomach (for some unknown evolutionary reason) generates lots of acid, and you get heartache.
All those folk tales where the jilted swain dies of a broken heart? Shoulda used Rolaids...Cecil touches on this in this column
Sounds like you’ve been lucky enough to have avoided either heart break, or heart burn, or you would understand the difference.
Real heart burn hurts, like, “time to go to the hospital” kind of hurt. Been there.
The broken heart just feels heavy, like a weight in your chest. I don’t know what causes it but I know what it feels like.
Either way, I hope your luck continues. 
Actually, as a veteran of both, I stand by my theory.