There are many reasons for a bulge after a tummy tuck. You shoud definitely see your doctor again to make sure you are on course.
Fluid collections may need to be drained.
Patients on narcotics tend to have slow bowel motility and more volume in their intestines.
A postoperative bulge may occur due to decreased motility for other factors as well.
It is possible the fascia was not tightened (hopefully not).
Sometimes, underlying anatomy such as a uterus, fibroid, etc. may become visible when lots of fat and looseness are removed.
Some patients have lots of fat insider their abdomen (intraabdominal fat), and the fascia can only tighten so far, so a bulge persists despite an abdominoplasty.
So there are some of the things that can result in a persistent bulge after surgery. Your surgeon can see if any of those apply.