It's hard to give advise over the phone but this is a favorite of mine. Proper hold with a fully drawn arm.
Next time you are at a shoot, watch the good shooters, their elbows point behind them. The mediocre shooters will have an elbow that is near 90 degrees to their body or somewhere in between on the way to proper draw.
Draw your bow in front of a mirror normally and see, then draw until you see your elbow extended back, you will feel your shoulder kind of " ball" up at a point. You may not feel your back muscles immediately but as you practice this draw you will begin to feel your back muscles along with that certain feel in your shoulder, a feel you don't get at lesser extension.
Your bow arm should feel like your going to brush the string on your clothes more so than out in front of you with too much triangle. This puts your bow arm into bad alignment.
My bow arm is extended and feels just like if you lean one handed on a post.
Just extended but not pushing into hypertension.
I hope this helps one person.
Good luck.