Ruff, I too wear glasses. IF the string is to the side of your face, I suggest that you are drawing too far back. for most shooters, the string will lie right on the lens of the glasses in front of your eye. When released, the string should go OUT(away) from your face, not move along the side. This (moving along the side of your face)would be the only way to "catch" the glasses and turn them onto a second projectile.
I suggest that it is not your head position that needs adjusting but rather your anchor references on your face.
As usual, need a picture to be sure, this is just a generic answer. Take a close look at my avatar picture -- you can see the string.
Arne