14 weeks after my tummy tuck, why is it taking so long for the swelling to go down? (Photo)

Tummy tuck swelling can take a few months to completely dissipate.  I really wouldn't worry too much about it.  Perhaps the one thing you can do at three months is begin some pilates classes and general working out.  I can see from the quality of the work that your surgeon knows what he or she is doing so I'm sure you are in good hands.Best of Luck!

It is not uncommon for tummy tuck
patients to stay swollen for an extended period of time after the procedure. Gravity
draws the lymph (tissue fluid) toward the ground, and it takes the lymphatics
time to recover and allow full absorption of this fluid. This can result in
extended swelling. Mild compression may reduce the swelling, but in time it
should completely resolve. Thanks for your question, and good luck in your
recovery.

The skin and fat are lifted at the level of the muscle and can disrupt the lymphatics that drain tissue fluid back into the circulation.  This will resolve over time.  If the swelling persists it may be subcutaneous fat that can be aspirated by liposuction. Your doctor has ruled out a seroma that can also cause swewlling.

“Swelling” 14 weeks after tummy tuck surgery may or may not be normal; it is best to be seen in person ( by your plastic surgeon) for precise diagnosis and treatment.   Generally speaking, 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.
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.
 Again, let your plastic surgeon know about the questions/concerns you have. Best wishes.

You might try weight loss and lower abdominal exercises. Maybe lipo??? Best to obtain in person second opinions.