Over on AT there is a Sticky at the tp of the general archery forum--author is a guy named Nuts-N-Bolts. Although it's mostly for compound bows there are some good pics and explanations about form. Pay particular attention to the part about how to grip a bow. It sounds like your grip might be at fault. Turning the hand out at about 40 degrees or so not only reduces torque, but also rotates the arm out away from the string thus eliminating or at least reducing string contact with the forearm. Also a contributing factor could be that you are over drawing the bow to some extent.
If in real doubt you can post this question in the Traditional forum on Archery Talk. Then you'll probably get some more educated responses.
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