Hi Jenny,
I had a double mastectomy in 2009 and reconstruction though my reconstruction was different to yours. I still get pain on the right side which was done in November 09. It seems it can take quite a while to heal after this kind of surgery. I was told I would have scar tissue that could be causing some of the problem. We are all different and consequently our healing time is different. It might be worth discussing the pain you are getting with your surgeon. There may be something that can help.
Hope things improve soon. Take care of yourself.
Caren x