I had this!
Go get a massage and have them work on your glutes, your iliac crest and your IT band.
Best money I ever spent, fixed me right up.
I don't know what triggered me to tighten all up, but that fixed it.
(I'd googled for answers, wish someone had recommended it, coming back to posts now to share since it worked for me)
Whenever you walk, make sure (a) lift yourself / your stomach up so you're not sagging into your hips, and (b) consciously 'engage' your butt muscles to participate.