Can you post a picture taken from the side like the model on the REI page?
I'd bet you a cup of coffee that the pack is way too big or the load lifters are cinched too tight, or both.
Seen below, the red arrow is pointing to what appears to the 'load lifters', which are cinched up very high and tight.
The strap should go over the shoulder - blue line - so the pack is resting on the hips and shoulders, while the load-lifters gives you option of pulling in the top of pack closer to the back of your head.
Try loosening these load lifters, allowing the top of the pack to start to lean away from your head.
So take it from me, an unknown stranger, go in and get fitted by the REI experts, like I did. If you can't do that, I'd go down a size and check those load lifters.
the yellow arrow is pointing to the load lifter, try and loosen that