I have an extreme fear of sudden cardiac arrest

So I have been suffering from this wired fear lately . I have an intense fear of SCA. I believe I might pass out any moment. This fear is really controlling my life . The worst part is that I can't seem to understand whether I have a physical problem or is it just anxiety? I have these wired feelings in my chest accompanied with 24/7 lightheadedness. I feel as if my heart instead of beating is wriggling . I sometimes have this episode where all of a sudden I can feel my heart beat in the chest but it's like a very paused and forceful beating like it beats then it feels like it stops for a moment and then again beats but it seems as if it's forceful. I have had TMT test , echo test blood tests and numerous visits to the doctor and to the ER but they always say it's my nerves . My psychiatrist also thinks it's Generalized anxiety disorder? What is it really and how do I get myself free from its fringes ? I am an 17 yr old whose life has been turn upside down literally by this incident .

Are you on any anti anxiety meds? I had the same feeling for a long time. Although it turns out I have a heart condition but is not life threatening. I'm recently doing a nuclear stress test today and tomorrow just to rule out any other problems. But go see a cardiologist. I had to get a second opinion on mine and I'm glad I did.

What condition do you have if you don't mind me asking

Diastolic dysfunction it's better then having systolic I've been told. But mines controlled with a beta blocker.