Swelling or seroma? I am almost 6 weeks post-op TT.

I'm sorry to hear about the concerns you have after tummy tuck surgery.  As you likely know, your plastic surgeon will be your best resource for precise diagnosis, advice, and the most meaningful reassurance...
Generally, abdominal wall "swelling" after tummy tuck may be related to:
1. Swelling in the soft tissues.  This may take several months to resolve and may worsen with increased activity  or at the end of the day.   Patience  is required to allow for resolution of the swelling. The swelling occurs because of the interruption of venous and lymphatic channels that occurs during the tummy tuck operation.
Often patients will like their “flatness” immediately after surgery; then, these same patients are disappointed for a period of time once swelling of the tissues occurs. In the longer term (this may take several months and even up to one year), the swelling dissipates and the skin of the abdominal wall "redrapes"  over the smaller underlying  musculoskeletal framework (where the abdominal wall muscles have been brought together again in the midline). 
2. Fluid accumulation in the space between the skin and the abdominal wall muscle.  this may consist of blood ( hematoma)  or serum (seroma).  This fluid accumulation can generally be diagnosed by physical examination ( occasionally ultrasound  may be helpful).  Treatment consists of aspiration;  several episodes of aspiration may be necessary. 
3. Separation of the abdominal wall muscle repair may lead to a swelling/bulge appearance. This may be diagnosed on physical examination  with your surgeon examining you in different bodily positions. One of the steps of a tummy tuck procedure involves reapproximation (plication)  of the rectus muscles.  These muscles have spread apart during pregnancy and/or weight gain. Bringing them together again in the midline helps to “tighten” the abdominal wall as well as to narrow the waistline.
4. Residual adipose tissue may be confused for swelling. Again this is most easily diagnosed by physical examination. Additional liposuction surgery maybe necessary to improve the results of surgery.
Generally, it takes many months for swelling to resolve after tummy tuck surgery and it may take up to one year (or greater)  for complete skin redraping  to occur.
I hope this helps.

It is pretty common for swelling to vary during the day. In most patients examination can determine whether or not there is fluid. If there is any question, I simple insert a needle to see if there is fluid. The majority of the time, there is not. If so, we decide how to deal with it. If there is still uncertainty, I will ask for an ultrasound.

HI thank you for your question. Its not possible to be sure on this forum but an ultrasound scan will be able to tell the difference. Its best to discuss it with your surgeon either way for advice and reassurance.Best wishes.