Why is my stomach not flat after tummy tuck? on the other hand the stretch marks look puffy and ugly why?

A "tummy tuck" usually is confined to the redundant skin and areas where the elastic portion has been stretched. If your "stomach is not flat" it may be secondary to fat deposits in your intestines which make the abdomen protrude. This can be corrected only by weight reduction with exercise and diet control.

This is likely due to swelling and Adema. Often times these can be improved or ameliorated by the use of manual Fattic drainage. You may want to discuss this with your treating physician and/or seek the skills of an experienced post operative massage therapist.