medici
I think you may be turning your upper body/chest, too far....this puts strain on the lower spine/hips and threrefore they react (in your case the lower sway)..
Try turning to about 70% of previous amount....
The backswing turn consists of 70-80 degrees of chest turn, with 20 degrees of shoulder blade movement, which gives you the full 90 degrees shoulder turn at the top......