Without seeing you on your bike, that'd be my first guess! I'm by no means a fit expert, but I was fitted on my bike by some guy who went to the Specialized Univeristy of fitting-ology so I guess I can be fairly confident my frame size is good for me. However, my fit dude was about my height, and he says he can ride a 58 cm or 60 cm frame no problem. But then, he wasn't proportioned like me. I also have longer arms, just a little fyi.

Yeah, lowering the stem effectively makes it longer (so I've been told). My stem was raised from -8 deg to +8 deg to effectively shorten it. Fit dude was hesitant in shortening the stem because: 1) probably didn't want to swap it out, and 2) said shorter stems result in poorer steering. You could also move your saddle forward but then that'll affect other things.

Anyhow, do you find yourself craning your neck while riding? What position is it in and where are you mostly looking?