I don't remember a significant difference in size, either, but it's been 15 years for me... I do, however, still have tightness and pulling around my "new" belly button, even after all this time. I'm sure it's from adhesions, but massage doesn't seem to break it up the way it has for the rest of my belly. Bernadette is right, it takes time for it all to heal, to stretch out, and to feel somewhat "normal" again. I would suggest going to a good physical therapist who is experienced in myofacsial release and who can teach you how to compensate properly for the loss of the abdominal muscles. Wish someone had sent me... I started having back problems a few years after the surgery, and much of it, I can attribute to the surgery. Most Plastic surgeons don't, from what I know, but I think it should be recommended for all mastecomy patients, regardless of the reconstruction.
"There's a difference between a philosophy and a bumper sticker." --Charles Schulz