What Causes Tenderness In The Stomach After An Abdominoplasty?

I am a 46 year old female, Active playing tennis a couple of times a week and I walk often. Point is, not sedentary. I had a tummy tuck 1.5 years ago, so my stomach is flat, however in the last 4-5 months my upper stomach has grown larger. In the middle of my stomach, it is extremely tender to the touch. I don t have an upset stomach, just tenderness. I have also gained about 10 pounds in this time and my diet has not changed. In fact, I probably take in about 300 less calories a day than before. I have become extremely fatigued and tire quickly and my sleep pattern has not changed either. I tend to get 6.5 - 7 hours sleep each night. My body always feel sore and my muscles ache constantly. Any advise would be helpful