Thanks for your reply. I have been to see the physio and has given me stretches for my left ql. I am also to use the tennis ball to release the knot. This is slow and painful process.
I am still doing the exercises i was given for my si joint which has improved the imbalance. I do bridging, leg lifts while lying on my stomach and butt clenches.
Many times while working at a desk posture becomes an issue. Individuals will tend to lean ever so slightly causing mechanical alignment abnormalities which contribute to muscle tightness causing the imbalance you mentioned. If your "QL" muscle is truly tight on the left then strengthening the opposite side is important as well as stretching of the left "QL". It would be best to consult with your physio regarding proper techniques to perform these exercises since demonstration is difficult on this forum.
Best in Health,
JAG