Chest looking like it has caved after double mastectomy

I had a lumpectomy Sep 2015 right breast,  and over the last six weeks have experienced when doing yoga or stretching my arms (it's on both sides) pulling and soreness over breasts and under both arms. The GP requested I have a CT screen which show up clear. I see the specialist both surgeon and oncologist on the 7th March, maybe they may know what it is. 
Lets us know how your result go. Waiting is awful but keep busy and take care.