Why are my underarms darker with foul odor?

I just recently had my breast reduction September 19th, I am now in 10 days out and noticed that my underarms are a lot darker than they were before the surgery, not to mention they carry this very foul odor! There's also some rashing going on, and my underarms seem to be more of a wrinkle versus being tight how they were before the surgery. Has anyone else experienced this after surgery? Can anyone tell me if this is caused from the surgery? If so, what is going on? How do I control it?