I always mention that when I'm well enough to exert myself in any way, I have some kind of crash that feels like something is going after my heart.
This is me too. I have mentioned this to several doctors over the years but it is not taken seriously since, as you say, blood tests and stress test/EKG come back normal. One doctor even screamed at me when I said I had "heart pain." He said he was sure he had some friends that had experienced heart attacks who could tell me what true heart pain felt like.
Also when he was titrating me up on thyroid meds I realized that the meds made me more "heart tired." My description for it. They must have been speeding my heart up too much and making it work harder.
It's like some of the times my crash fatigue actually originates from my heart especially when I have been pushing myself to do too much. I think and fear that whatever caused the ME/CFS, is causing some damage to my heart as well.
Is that how you feel, @lukesirde?