What can I do about having an extra beat? Is this benign?

I have been suffering with episodes of having extra heart beats.  I have had a holter monitor which showed an extra 2000 beats for that 24 hour period, and have had a chest xray, and prior to that 3 years ago a stress test, and heart ultra sound.  I have also had various ecgs done.  The ultra sound showed I had a mild mitral valve prolapse and that was it.  These episodes occur about every 6 months or so and last about 2 weeks.  It generally starts in the middle of the day and progressively gets worse. 

When I last visited my gp in Feb 08 he told me that the electrical pulse for my heart beat is starting in the middle of my heart instead of up top and it is totally benign and not to worry.  He gave me a script for xanax to help me not be so anxious about it.  But I feel even anxious about taking the xanax and am concerned that something is wrong that could be fixed.  I get a mild chest pain at times with it and is frustrating me!  I only have caffeine in a cup of tea about twice a day .  Can somebody please give me some advice??  I live in Australia. My heartbeat is not faster than normal at all just has extra or skips beats.  My grandfather had 3 heart by passes and died of a heart attack in his early 70's.  My cholesterol in normal and I am in the normal weight range. Thanks for any advice or help given.