" I told myself to just relax & shoot comfortably" Bingo!!!! Don't use ANY muscle not required for the shot.
In general, your draw length should not be arbitrary. It should be the result of alignment at full draw, and I like to favor "bone on bone" alignment. Your facial references for your string hand are a RESULT of the draw, NOT a target OF the draw.
There is a place where your string hand is anchored on your face, AND you can continue to increase back tension WITHOUT your hand or string moving back any more. That's because your string shoulder and upper arm are moving perpendicular to the arrow line -- towards your back. NOT straight back along the arrow line and away from the target.
If you haven't looked a some videos I did a while back, see if they give you any ideas to try.
http://www.youtube.com/user/TheMoebow1 Arne