It sounds like what you are describing is lateral epicondylitis. Without being able to see the area and actually touch and stress the area, that would be my guess. It can be caused from overuse and by repetitivelifting of something too heavy. It can happen at the ligaments at the lateral epicondyle or the tendons originating at the radial head and lateral epicondyle. I would suggest decreasing your shooting for a while, take an NSAID like ibuprofen or naproxen, and ice, ice, ice. This is a nagging injury that can takes months to resolve, but you have to eliminate the cause. My guess is the bow being held out for extended periods of time and the slightshock transmitted to the arm is aggrevating, if not causing your symptoms. They make a strap for "TennisElbow" that actually puts the tension more in the belly of the muscle than at the origin to distribute the stress where it is better tolerated. It may help for a while to get you over the hump. Just my educated$.02 worth.