My but is high up my back 6 weeks post-op, do I need more liposuction?

It is hard to say without at least seeing photos. I will say that there is an art to shaping the buttocks/hips with a BBL and some body types are more difficult than others. There are more than one desired result by patients, so it is important to communicate with your PS what your goals are. The shape you have may be what another patient would be really happy with  while it is not what you wanted. 

It's difficult to get a full understanding of your case without photos or a consultation.  It sounds like you may be a candidate for Vaser revision.  Vaser is the only technology that can remove both the superficial and deep fat layers to maximize contour and symmetry. A buttock assessment tool to get an idea of the shape and projection you'd want.  Contact a Vaser specialist, via Skype or Facetime, to get a better understanding of your case.