Hip Bulge on One Side

Without a face to face physical examination much less a photograph there is no ethical way we can begin to answer your question in the mannere it should be answered.

Side fullness after a Tummy Tuck is related not so much with what was removed but with what was left behind.

We are three dimensional creatures. Unfortunately, a Tummy Tuck addresses only the front of the abdomen. If you have excessive fat on your hips and back with or without skin excess, removing the skin and fat apron in the front will only unveil this excess, The side fullness you seem to be unhappy with is most likely excess skin and fat which were not (could not be) removed with the tummy tuck.
In your case, the surgeon is "chasing the dog ears" sideways but not winning because you most likely would have benefitted from Liposuction of the back and hips before or at the same time as your Tummy Tuck, from a Lower Body Lift procedure OR at this point from a Buttock Lift.

Without a photograph it is impossible to be sure. I have extensive experience in this area and I am still repeatedly amazed on how many women see only the loose front (2 dimensional view) rather than recognize the 3D features and challenges to JUST performing a Tummy Tuck and temporarily ignoring everything else.

Dr. Peter Aldea

A bulge after a Tummy Tuck procedure could be fluid under the skin that needs to be aspirated.  I would give it some more time to heal since it's only been 3 months and full results can take up to a year.