I keep getting weird flutters in chest and yesterday I got a major thump in the middle of my chest which triggered a panic attack ofc. I had full blood tests and one specific for heart tissue, several ecgs and holter monitor but nothing happened while I had it so I don't suppose anything will show up. As well as that I get weird pressure in my head and chest every time I get up ( i am laying down a lot ) and sometimes when I walk I feel lightheaded. Doctors say it is anxiety, but is it possible to be something that they cannot catch from these tests? And has anyone else experienced this?