Wow a picture really can be a thousand words !!!!

My first thought is that your load lifter straps are too tight. What do you feel when you loosen them? Too much weight on the shoulders? If that's the case take the load off your shoulders by shrugging them and then cinching up your waist belt.

Also....the point where the shoulder straps attach to the pack looks a tad low. Is that adjustable?

I have no personal experience with your pack but it looks like a nice one. However it is possible, as with shoes, that this particular pack does not work with your particular body. But I would play with the adjustments more before drawing any conclusions. If possible I would have an expert (unlike me) check you out in person. We can only guess so much over the internet.