Yes, your instincts are correct. Find a new doctor, an electrophysiologist who specializes in irregular heart rhythm. If your cardiologist is already an EP, still switch. Sounds like yours has checked out.
It has been noted by my EP that most patients feel the heartbeats while trying to sleep. We are focused on it and there are no other distractions. There is no reason to think that your arrhythmia begins at night in bed other than the stress you feel. It can become a habit. Trying falling asleep while reading or watching TV as a distraction from coding on your heart. Good luck.