Butt uneven after BBL due to massage 10 days post, what alternative options do I have to correct this? (photos)

Ideal candidates are at a stable weight,  in good health , and have excess fat in some parts of the body and too little in other regions.  Gaining weight before the procedure is to no advantage and when you lose weight again the fat cells will shrink just like the donor site fat cells.  Typically, the transferred fat results in a significant increase in volume of the body site being treated.

You should definitely notice some early differences between sides.  It sounds like you should clarify with your surgeon your concerns.  Fat grafting entails taking excess fat from the areas of your body you consider problem areas and transferring it so that it has the best chance of survival.  This will help add shape and volume.  There is a period of recovery needed for the fat to settle and make its home in this new region of the body. It does take time for it to soften and also for the skin to relax under some of the stretch. Again, I would advise consulting again and/or considering obtaining a second opinion.