well stance is very personal. It really comes down to what you like. It might even change as you progress as a rider. But To see if it is a pressure thing related to stance try angling it more out. Maybe instead of putting pressure on the outer side of your foot you can move the pressure to be on top of the foot.
Also switching bindings might not hurt either. You're just going to have to experiment a bit. It might come down to a boot issue. Maybe the shape just doesn't go well with your foot. who knows.