i think the back pain is a separate issue.
your body is like a computer and sometimes it tells you that something is wrong.
and doctors dont know the answers to everything. when my heart was racing. my doctor asked me did i have a bad dream, do i drink coffee, did i take asprin.
he assumed it was the coffee and asprin (caffine).
but i have a friend that had problems with his heart (this happened to him and his wife months apart)
he went to the hospital and they told him his arteries is clog with plaque (veins of the heart is clogged with cholesterol) he had to get stents (they had to flush it out).
if you go to the doctors let us know what happens. if you have no insurance i would go to the emergency the next time it happens.