I don't think docs tend to worry about meds like Cymbalta for abuse. It's the opiates that they are generally concerned with.

The Cymbalta could have been reducing your symptoms, or you maybe didn't reduce slowly enough and are experiencing withdrawals. It can be a powerful and effective med. It caused me severe stomach pain after being on it for a while, but it's also the med I regret most not being able to handle since it worked so well!

It's also much harder to reduce pain once it's elevated, so you're reaction isn't surprising. You didn't say how long you were on Cymbalta for? What did you feel like prior to being on it?