I get an agonizing pain in my left shoulder and neck while riding after about 1 hour. I can't turn my head to see traffic without feeling like someone is stabbing me with a knife. I usuually have to stop and stretch out, but that only lasts 15 minutes or so. I am doing a 72 miler next month and am worried this is going to slow me down. Any ideas on how to alleviate this problem while riding? Its only in my left side side.