What you were describing fortunately does not sound like a heart attack both symptomatically and the fact you state you are in good health and without family history of such. While not all people present with the "classic textbook" symptoms.. usually the symptoms of a heart attack are;
- a tight or "squeezing" type pressure in the chest. Some have described as 'an elephant' sitting on their chest.
- diaphoresis (sweating)
- pale and/clammish skin
- rapid heart beat
- dizziness
- shortness of breath
- radiating pain into the left arm and/or jaw
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there could be more or less symptoms, and again, not all people present the same. Anyone ever feeling those symptoms above of course should immediately be checked out and not even consider posting on a forum but run to the local ER.

Minnie_me, I would say likely based on your age and such, likely it's 'growing pains' or likely associated with reflux. A hital hernia could be another possibilty causing the discomfort. Stress, anxiety, and lists that could go on and on could be other possible causes. Something you may want to try next time you experience the discomfort might be a product such as Zantac and see if that makes a difference.