I can't comment on the use of duloxetine for your particular issue, but I can sound a warning note about its addictive qualities. My wife was prescribed the stuff by her neurologist to help with dystonia issues but concluded after a couple of years that it didn't really help. She has been working with her GP to reduce dosage and eventually come off it, but the side effects of extreme fatigue have caused them to pause the weaning process until after the festive season. Then the plan is to transition to another drug which is more easily weaned.
So if you must use it, beware. Those who prescribe it rarely have to confront the issues involved in coming off the drug, which is a great shame.