"...but what to do."
You're doing it!
You've had the tests and been told there's no reason for concern. You're having an echo for extra reassurance. Trust the medics. Listen to what they say. You say you've posted about this problem before. Presumably you read all the threads on this topic? Then you'll have read that ectopics are common and normal and cause no damage.
Sure they can be a bit alarming to start with but people learn to live with them and eventually don't notice them at all. Cut out caffeine, cut back on alcohol, try some of the other suggestions mentioned here and on the earlier threads. But if after trying all that you still have them then you need to start being relaxed and accept them.
What's probably happening here is that even after nine years you still haven't accepted they are harmless so when you feel one you get a big shot of adrenaline which then makes everything worse. Next time you get them try some physical exercise. For one thing, exercise can sometimes quieten them down. If not then at least you'll be reassured when your heart responds perfectly normally, that you're not about to keel over.
Good luck with the echo.