Get examined by your surgeon
You should see your surgeon for an examination. This could be a seroma, or excess tissue that may not have been adequately removed during surgery. Either way, it is important that you discuss this with your surgeon.
"Big on Top" after tummy tuck
It is not uncommon for patients to experience months of swelling after abdominoplasty surgery, and often it is most apparent below the umbilicus. Nevertheless, it would be important to make certain that you don't have a seroma, or fluid collection between the soft tissue and the muscle, and nothing substitutes for close follow up with your surgeon to ensure optimal post operative results. I would suggest that you make an appointment for an assessment and thoughtful physical exam, so if there is a fluid collection it can be addressed, and if there is not, you can discuss your concerns, as well as a plan to improve your results. Best of luck!