By not using your legs to get a feel of how they should move as you swim you have made the first step in the right direction . To help keep the legs and hips light and floating right along behind you also try :
rolling only enough to clear each shoulder as you roll and not to stacked shoulders . Over rolling can make your legs splay outward to try to compensate for being unbalanced
Lean in to the water always as you swim.
Look down keep your head in a neutral position and relaxed
Keep the legs stretched out without to much knee bend
spearing in to the water with hand below elbow