It sounds like you might do good with a little counciling and maybe being on some anti anxiety medication unti this all passes.
When you focus on a problem weather real or imaginary it then becomes real and you start stressing with all the what if's.. I've known people that sit and take their pulse almost non stop day in and out, as soon as the heart skips a beat or as soon as their pulse reaches 150 they call 911 convinced that they're in the middle of having a heart attack.
People at the hospital have blood drawn and the checkd the blood pressure to check for the enzymes the heart puts out when it is stressed or having a heart attack. Any electrical disturbances, or blockages will show up on the ekg. If your heart sos a beat or two, that's normal even babies hearts will either sip or do a double heat here and there, there's no pain, no other symptoms and the majority if people do not feel it
If your EKG is normal then you're doctor sayw your suffering from stress and anxiety then that's what it is. With getting yourself worked up to a state thinking your having a heart attack, you will feel chest pain, you will be short of breath, anxiety makes the adrenaline. In turn the pumping adrenaline makes your heart beat faster your heart starts beating faster it already tells you everything is running too fast. With the adrenaline rush you start feeling the chest pain, become short of breath it's a normal reaction.
By comparison let's pretend you're home alone and you go to get something out of the kitchen. Suddenly someone Jumps in front of you startling you badly because you knew you were home alone... it's very scary at first ... your initial reaction is to jump back and probably scream ..... the next reaction you find is your hands are shaking hard, you start sweating for no reason, you have not been exerceising so why the sweat? your hearts racing in your breathing hard kind of like symptoms of a heart attack, but you don't have that chest pain. you're not gonna die however you're shaking so hard you can't understand why. that is the adrenaline rush you feel when you think you're having a heart. If your startled hard enough you could possibly pass out, but aside from a fast heart rate and anatural overdose of adrenaline everything's fine. If you then panic on top of that and then think it's your heart, another adreniline release is done to help your body handle the added stress even though your body's been fooled by the startle reflex.