Four months after surgery the results are pretty stable. Garment to use at this point is useless. Weight-loss strategy is reasonable but revision surgery may be another measure that needs to be discussed.
If you have an area of fullness of the upper abdomen at 4 months post op then this may be residual fat. An exam would be necessary to tell if additional liposuction would be beneficial to smooth this down. For safety reasons this may not have been liposuctioned at the original surgery.
At 16 weeks you are 99% healed so try losing weight and exercising are great alternatives. Seek IN PERSON opinions..
Most plastic surgeons use compressive garments after body contouring surgery. Their ultimate benefit is not been determined but it's a small sacrifice to where these. Final resolution of swelling will take a number of months.