afraid to take

I was prescribed metoprolol succ er 25 mg tasan. I have not yet begun to take it. I just had surgery for Wolff-Parkinson-White syndrome and have been having more skipped beats and palpitations now then ever before. They told me that all ekg's are fine. They see them on the ekg's but the are harmless. They feel the wpw is cured. I don't understand why I feel worse now than before. I started xanax about a month ago. The doctors said maybe stress was causing the problems. I have stopped caffeine and alcohol and have been drinking a lot of water to try and stop them. I know that I should try the beta blocker but with the side affects I am afraid to try. Anyone out there with pulps that takes this and is doing better?