sounds to me like you are pulling on the string instead of with your back.
if you feel like your elbow or shoulder are being pulled out of place when drawing get someone to show you how to properly draw.
your wrist,elbow and shoulder should be locked in place and you contract your back muscles like you are stretching your arms wide.
remember at first you can draw more weight by just using fingers than with a release, i was drawing 70 lbs with fingers add release and i had to drop atleast 15 lbs off that draw weight, I am adding pounds back on a little each week