I'm wondering if I get a BBL if it's going to look unnatural?

Without seeing photos of you out of clothes it's not possible to give you any recommendations. Consult in person for an exam to determine if you are a candidate or not. Fat transfer is a great way to create a rounder buttock, but your final outcome depends on the quality of your skin and your anatomy.Best wishes,Dr.Bruno

Typically liposuction of the abdomen, sides, and back with fat transfer to the buttocks and hips produces a nice result. It's difficult to tell from the three photos (jeans/sweater) you provided.Kenneth Hughes, MD, Board Certified Plastic SurgeonLos Angeles, CA

Hello, thanks so  much for your inquiry and for your interest in this procedure. You have already a nice shape but of course it could be enhanced with fat injection. The pictures you have provided are not very clear in order to have an idea if you have enough fat donor sites but in the case you do, you will achieve a beautiful result.Please make sure that you and your surgeon are on the same page. Don't forget to discuss all your concerns, options and expectations thoroughly. Have a safe and pleasant PS Journey!Respectfully,Dr. Jaime Campos-LeonBoard Certified Plastic SurgeonTijuana, BC Mexico

A Brazilian butt lift is a safe and effective procedure that combines liposuction of the abdomen hips waist and back and then fat grafting to the gluteal region. This is a safe and effective way to contour the lower body. After a successful Brazilian Butt lift, the fat that remains will stay there for the rest of your life. Like the rest of the tissue in your body this fat will grow and age with you.The common donor sites for this procedure is your posterior waist/flanks, lateral thighs, back, waist, and anterior tummy.Choose a board certified plastic surgeon who has done a ton of Brazilian Butt Lifts and has privileges to do this surgery at a local university hospital. This says his credentials have been checked out by fellow Drs. All surgeries carry risk, talk to your plastic surgeon and choose one wisely.Many surgeons, including myself, offer online virtual consultations where you send us your photos and we can estimate the cost. I, like many surgeons, also offer free consultations so that you can be examined and given the most accurate quote.

Dear Ms. Lingglingg,Thank you for your questions and information.
Nothing substitutes for a personal evaluation and a face to face discussion of your options including a review of your medical history/medications  and a face to face discussion of your options.
Unfortunately with out nude  photos or a exam of your tissues I can can only comment based solely your photos. However, hopefully you will find them helpful.
The final shape and appearance depends not only fat injection but also shaping the buttock with precise injection of fat but also selective liposuction of the tissue around the buttock. 
The process for performing a BBL is the same regardless of the patients weight:1) harvest the fat 2) purify the fat3) inject the fat
The amount injected depends on how much fat there is available to harvest.One can try to gain weight prior to the procedure in hope that the areas you can the weight can be liposuctioned.
Caveat: not all fat gained can be liposuctioned.
Please make a appt. with experienced Plastic Surgeon who is Certified by the American Board of Plastic Surgery and ideally a member of the American Society for Aesthetic Plastic Surgery (denoting by membership as having met additional criteria and a focus on Cosmetic Plastic Surgery).
My best wishes,
R. A. Hardesty, MD, FACSDiplomate and Certified by the Am. Bd. of Plastic Surgerywwwimagineplasticsurgery.com4646 Brockton AveRiverside, Ca 92506(951) 686-7600