I'm so sorry you have those annoying ectopics too. I get them too and mine are not related to anxiety. The way it works for me is that the hard ones are PACs and the soft ones are PVCs. I'm not sure if your body reacts to them the same way but you could ask for a 24hr/48hr/30 day monitor to check what they are. Have you had an echo? If your doctors won't do an echo and let you wear a monitor, go get a second opinion. It's important that your doctors know what it is that you're experiencing and rule out potential causes. You probably want to get your thyroid checked out too. Thyroid hormone imbalances can cause this too.
My palpitations have been thoroughly investigated and they are benign. I don't get them when I'm anxious either. I get them at random times even when I'm super calm. In the past the seemed to be related to my vagus nerve. I would get PVCs and PACs when it would get irritated. I recently started getting more frequent (unifocal) PVCs and they seem to be related to hormone imbalances and bradycardia. I get them around the same time every month when I'm trying to sleep and my heart rate drops below 55 bpm. Sometimes they wake me up at night or prevent me from sleeping (my heart often kicks me in the chest all night long, fun fun fun). So yeah, they suck!