I hope I can reassure you a little when I say I have had ectopics since I was in my 20s (I'm in my 60s now!). I used to be terrified by them. Developed full-on 'cardiac neurosis' - was convinced my heart was going to stop at any time. There were times it was all I thought about!
I still get the ectopics, especially when I lie down on my side to sleep, and if I have or have recently had an illness (particularly covid. I measured something like 15 an hour one particularly bad post-covid weekend.) They feel as if my heart stops for a second - then rebounds with a really strong and startling beat, out of time. Unpleasant but honestly you do learn to take no notice of them.
In all those years, I have never had a heart attack (which I worried was so imminent, 4 decades ago!) or any other heart-related conditions. I have had a few ECGs including one recently, and structurally there is nothing wrong with my heart - I no longer worry about them at all, they are just part of me.
I hope this is at least a little reassuring, bless you, I honestly know how horrible a time it can be when one is worried about them - dreading them - fearing what they may mean. Of themselves, they mean - nothing.
I don't know if it helps you at all, but it helped me when I was told the heart is 'just a muscle'. Not really that fancy. It keeps on and on and on beating even if the signals go a tiny bit awry at times.