I understand your concerns about your appearance, and your desire to change it. You do have medical options for changing your appearance, but it will be worth discussing these options with both your primary care doctor
and a plastic surgeon
To answer your question directly, it is possible to re-cycle fat cells from one part of the body to another. The fat is taken from the stomach, removed, and goes through a special process called "decanting" prior to re-injection in the desired area (often the face or buttocks). The quantity of fat that can be removed and re-injected is limited, and requires a plastic surgeon trained in this technique. You also have the option, however, of liposuction
(removal of fat) in your stomach, as well as surgery, typically silicone gel, implants, or shaping liposuction, to improve the appearance of your bottom.
That said, the decision to consider plastic surgery is a serious one. There are risks associated with the procedures including but not limited to undesirable cosmetic outcome, bleeding, and infections. Additionally, cosmetic surgery is often not covered by US insurance, which would require you to pay the full costs by yourself. There may be other ways to achieve the cosmetic outcome you desire through diet and specific exercise. Before deciding on any surgery, you should have a discussion with your primary care doctor and a plastic surgeon about the specific cosmetic outcome you are seeking and the ways in which they can support you in those goals.