Without pictures, it would be hard to determine the possible approach to address your concern. But for the sake of shedding some light on the issue, let me explain the basics of buttock enhancement surgery.
* Butt lift. If there is loose skin due to aging or weight fluctuations, a direct skin excision is necessary to reshape the buttocks. All efforts are made to place the scars within the natural folds of skin (groin, gluteal crease, etc.) or at least concealed by the patient's underwear.
* Buttock implants. Solid silicone implants are placed above the sitting area; hence, only the upper half of the butt cheek is reshaped and augmented.
* Brazilian butt lift. In essence, this is reversed liposuction or fat transfer. The procedure collects donor fats usually from the waistline--i.e., lower back, flanks, abdomen--which are then purified before they are re-injected into the buttocks.
Occasionally, these procedures are combined to achieve optimal results.
You may visit the attached link to view some photo references (Brazilian butt lift before-and-after photos).
Good luck and best wishes.