I always think with heart palpitations issues it's always best to call the doctor's office and report new symptoms. For many years I had palpitations. Over the years, at different periods, I had it checked out. Nothing serious, skipped beats Then around three years ago, really bothersome episodes of palpitations and a racing hear that made me feel anxious. Checked it out and told nothing to worry about . Atrial tachycardia I could take diltiazem or treat with magnesium. Chose magnesium and for about four months everything settled down. Then a flare up with lots of palpitations lasting for hours and a super racing heart that started just from walking quickly. I let this go for about a month! Did a holter monitor and this time it picked up ventricular tachycardia which does need to be treated. (on metoprolol).
So for many years my palpitations were annoying but not anything to worry about until a few years ago. Skipped beats are usually nothing to worry about. It sounds like you have been investigated. Ask about magnesium. Some cardiologists do recommend it for regulating the heart rhythm. And call your doctor if you are still worried.