Perfectly normal. They are called ectopic beats and are prevalent with us anxiety sufferers, Sometimes they are sporadic, sometimes they come in clusters, sometimes they stay for a few days/weeks. I literally had an ectopic every 4 beats, every time. Super odd but that was 10 years ago and i'm still here. Stress is the main cause of this so please try not to worry, it's benign, harmless and will sort itself out. It is NOT a sign of heart troubles.