I Was Diagnosed With Afib 10 Years Ago And Have

I was diagnosed with afib 10 years ago and have had good success with atenolol and felcainide 50 mg 2 or 3 tabs a day. 3 years ago I developed sinus tachycardia for unknown reasons. My doctor asked me to increase my flecanaide back up to 3 tabs a day but I feel it's making me nervous, at random times throughout the day. I'm at least somewhat calmer overall at 2 tabs per day. Is this possible?