Look i have seen many people hit their arms while shooting even with the correct draw length. check you draw length then check your grip. you should not be gripping the bow by clenching a fist. it should rest in the spot between your thumb and your index finger. with yourt hand just slightly turned from horizontal. do this actually in front of you when you read this make a fist (knucles pointed out away to the left for a right hander) then change it to my type of grip ( see pic ) watch your forearm move away from where the string would be try this it will be more accurate ( you cannot torque the bow) and you should not hit your arm