Your toddler subconsciously controls the weight you carry, so it is even more important that the backpack feels right. These are the most common problems.
Tighten up the hip belt and release shoulder straps a bit, so more weight rests on your hips.
Tighten up the load lifters. If the backpack still pulls, then slightly tighten up the shoulder straps.
Shorten the torso length. One loop can be enough.
Release the sternum strap. It should not be tight.
Extend the torso length, the hip belt most likely doesn’t sit on your hip bones, but a bit higher.
The following page will help you with the adjustments. - How to fit Panda Carrier