ghetto:
you have leg loading discrepancy which comes from a weakness/lack of mobility/lack of stability in the hurty side so if you have had an injury on that side then there's your problem
you'll also have less glute activation/strength on that side too
the worst part of this is that now while also having a weak side, now you'll get an overly tight side from too much loading on the non hurty side which is the onset of injury
raptor - i think your glutes just aren't up to par activation/strength and muscle quality wise...get some soft tissue work done than the minute that finishes stretch the glutes, adductors, quads and hip flexors then activate those glutes as best you can...it also seems that you're lower back is over worked when loaded (squats, deads etc)