Can I use neck pillow instead of BBL pillow?

Best to ask your plastic surgeon for his/her recommendation. I recommend that my patients minimize sitting, even with a pillow (boppy or BBL), for the first two weeks. If they must sit, every 30 minutes or an hour, they should get up and stand for a few seconds to take the pressure off. This reduces the chance for fat necrosis. I usually recommend about 6 weeks before sitting without a pillow. After 6 weeks the fat has revascularized, and they will have a very good idea of their final results.

Dear Neat345016,
I instruct my patients not to sit for 2 solid weeks. We provide them a specialized pillow that our patients can sit on during that time. They can sleep on their stomachs or sides. Fat viability depends a lot of surgeon technique. The fat has to be placed back into the buttocks as soon as possible so that it has a greater chance of survival. It has to be placed carefully so that not too much fat is placed in only one area.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery