I have been reading the answers so far and the most obvious has been missed !!! Indigestion
! that mimics heart pain perfectly !!
It is also possible that you suffered a heart attack
in your sleep ! a blood test
will reveal this !, the test is for cardiac enzymes which are released into the blood from damaged heart cells ! The heart attack theory is unlikely though so I would go for the indigestion !!
The bottom line though is---
You MUST see your doctor who may send you to a cardiologist!!
ACT now if only to alleviate your anxiety