Your brain can wreck havoc on your body. You need to accept what the doctors are telling you and try to get on with your life.
You've developed a phobia. It's probably the root cause of any exercise anxiety issues you're having. I went through this too. The only way I know to overcome a phobia is with a cognitive behavior approach, or intensive exposure therapy. I did this on my own. I went from not being able to exercise since 2009 to running 5ks in 20 minutes, right up until I messed up my knee :(. Sure I have PVCs come and go and they would command my attention. Kept going through it and focused my thoughts on other things.
P.s., another their thing that reassures me is all the tests I've had done over the years and how long I've had the condition. No changes, and if it were something serious I'd be dead by now. So there's that, lol. Seriously, that's what I focus on when they act up and I find comfort.