Although it’s difficult to advise you on which plastic surgery procedure would best help you without seeing photos, what you’re describing sounds like an isolated problem spot of fat. Liposuction is a body contouring procedure that’s optimal at targeting diet and exercise resistant fat in people who are close to or at their ideal weight. Many people have stubborn pockets of fat that can gather in specific areas of the body, such as above your buttocks as you describe. Schedule an in-person consultation with a board-certified plastic surgeon so you can better explore your options. Best of luck to you.