What you're describing is quite unusual unless there was work done on your buttocks. The first step is of course to follow up with your plastic surgeon.Best,Mats Hagstrom M.D.
It is rather unusual.A tummy tuck should not make your buttock look flat.When doing a TT, we usually do lipo of the lower vack and flanks.It is a great opportunity to do a fat transfer which adds curves to the buttock.