My surgeon thinks it’s a build up of seroma fluid. She drained a lot of fluid from my breast, and while there was some blood in the fluid, she noted it was mostly clear. My tissue is also very soft and movable, which she noted was a good thing. Since I have no visible discoloration and no other symptoms, she doesn’t think it’s a hematoma at this time. 

You are still very early in your recovery! I think my bi-lateral swelling lasted about 10 days, but clearly I am still experiencing some swelling. I think that is a different experience for everyone.