How do u help health anxiety with POTS

I have suffered with anxiety from an early age, i’ve always been overly anxious but it’s mainly been with my health and social anxiety.

For some reason whenever i get a flare up, i get this feeling of impending doom and that im going to die soon and the doctors have got it all wrong. I haven’t been diagnosed yet but ive seen a cardiologist and have had multiple ECGs and currently going for a few more tests before diagnosis. I know my hearts healthy except from POTS because of the amount of ECGs i’ve had, but something deep in my mind is always there telling me i’m going to have a heart attack or heart failure and i’m going to die, or my dizziness is a hidden cancer instead of heart related stuff. I give up. My mind is not my best friend at all but is my enemy. I’m just trying to convince myself i’m not gonna die in my sleep from heart failure or that i don’t have cancer. This shit got me checking my whole body for any lumps which i can’t find any but i still believe it could be cancer even though no doctor has ever suggested it and all doctors have suggested it’s POTS. its only because i read online that dizziness is a symptom of cancer it’s freaking me out. And heart failure because i get very bad chest pain.

Does anyone have any advice on what i can do to calm myself down when i get these panic/anxiety attacks. I’ve never really got help with my mental health before i’ve tried but got rejected by multiple places because i wasnt “bad enough” and they had too many customers and it’s only getting worse again so idk what to do anxiety is my biggest enemy.