Saggy butt after BBL. What can I do? (Photo)

I had BBL almost a year ago and noticed that my butt looks like it's sagging. The bottom part is no longer rounded, it now looks flat -- up close it looks a little triangular (not sure how to properly describe the shape). My weight is the same and I followed all of the instructions my doctor gave me. I even wore a custom faja and used a BBL pillow. I also made sure to sleep on my stomach. It didn't always look saggy so I'm not sure why this happened. Any insight would help, thanks.