The leg length thing ...... you can have up to 1cm difference normally due to bone length, having a smaller hemi pelvis, that is know as a true leg length difference. you can also have an apparent leg this is more down to how everything interacts with each other, it can result in a relative difference in how the two halves of you pelvis move(think of it as your sacrum as an axel on a car.... with the two halves of your pelvis on either side. when you do a symetrical movement eg bending forward they should move together, when asymetrically they should move independantly eg walking. some Wikipedia reference-linksij problems are due to the fact that they move the wrong way round. ok physios its a simplistic view but bear with me)
when you walk look at are you taking a slightly shorter step with one leg (don't measure listen to your cadence/rhythum which should be even). there should be some stretches that can change this. however, this is a first aid fix to help wiht the discomfort, it won't sort the problem as you still need to find out why this happens