I also have been dealing with this same issue for a long time. I went to see a sports doctor and had some x-rays done the conclusion was that I had a FUNCTIONAL leg length difference. Which means when they measured my bones they didn’t find a significant difference between them but somehow my body was creating a leg length difference. When I looked at myself standing I could see one hip bone was higher and also more anteriorly tilted. It frustrated me for a long time because after getting diagnosed and getting treatment from a physio, osteo, and chiro they all concluded the same thing but didn’t really get to the bottom of it.