Here's another thing to possibly consider... Hiatal Hernia...!
I had my first major attack over 20 years ago, at about 35, and I thought it was the "big one"... but after all testing with no clues what happened, tests finally found out it was a Hiatal Hernia rupture.
While no immediate surgery was ordered, further testing down the throat revealed my chronic swallowing and acid reflux problems started Barrett's Esophagus pre-cancer conditions and worsened hernia problems.
Since then I suffer frequently, sometimes daily, from symptoms exactly like a severe heart attack, with pain through the chest from the diaphragm, up the neck, and down the left arm.
Another scope down about six months ago shows worsening, but the surgeons still don't want to do surgery because the risks and complications are too questionable.
So I have to deal with my 'heart attack' several times a week, and have to eat very small bites slowly and carefully so as to not pack the hernia and burst the esophagus.
If you have ANY kind of similar eating or stomach problems this could be your explanation...?