I had this same thing the day after my surgery and was told it was my signal that I'd eaten too much too fast. I'm pacing myself as far as food goes and writing it all down along with the times I do everything, so that I can keep track of what works best. Since I started doing that, I have no pain and when I take a deep breath I can feel it in my ribs. my nurse said it's because I'm not taking 20 minutes for a meal, I'm just in too much of a hurry. losing a pound a day though.