Sacrum part of my back juts out more than it should causing back pain, would a butt augmentation help? (Photo)

It sounds as though you have pain in all positions not just while laying down on a otherwise retroflexed and prominent sacrum and coccyx bone. In cases where patients have had pain while just laying down on a prominent sacrococcygeal bone, I’ve been able to utilize buttock implants and/or shaving down of the coccyx bone with significant relief of pain and good overall success. Although a virtual consultation is an option, I believe an in person physical exam would be much more helpful in your case to decide whether this type of surgery could be of any benefit for you. Glad to be of help.

Dear pblaschka,
fat transfer is a cosmetic procedure which will not affect your sacral pain. I suggest you to visit your doctor and get an examination in order to find the right cause of your pain. 
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

I have successfully corrected this type of issue with buttock implants. You will need an in person consultation to determine exactly what needs to be done. Please be sure to choose a board certified plastic surgeon who specializes in this procedure and is well known in the medical community.