I have a shorter right leg and am constantly adjusting my stirrup length. I feel like my right stirrups is so much shorter that I'm putting my weight on the outside when I turn left and that is causing my saddle to shift to the left coming around the turn.  What are you doing so you stay more balanced in your saddle? I can tell I don't always sit square... My hips are off too and yes, I do go to a chiropractor. 

Have you tried a "Roper" cinch or a neoprene cinch??  I feel like both types of cinches hold a saddle in place better than most.