John Williams, MD

Most likely the sutures used to bring together your separated rectus muscles have broken. This can happen if there is a sudden increase in intra-abdominal pressure after surgery (like a sneeze or vigorous cough) or the sutures were placed under too much tension, or both.

It is doubtful that you are rejecting the suture. 

Your best option would be to return to your surgeon and discuss your options for treatment. The sutures can be removed without re-doing the tummy tuck. This can even be performed endoscopically.

Good luck, I hope this helped.