You have already received the best advice from Bear...I would only add that there are many antidepressants to choose from and if one doesn't work,your doctor can find another. But you have additional choices, you can seek psychotherapy which is a very effective treatment for depression.
You need to make sure that you are telling your healthcare provider about your past drug use. That's very important. You also need to keep them apprised of your mental health, if you are still feeling depressed, Cymbalta may not be the medication that you should be on, or you may not be on the correct dose. Keeping an open line of communication with your doctor is going to to be the key to a full and successful recovery. You may also want to join NA groups to help deal with your previous drug use, as this could still be playing a key role in your emotional state, even though you've been clean for two years (which, by the way, congratulations!). There is hope for you, but you need to let your doctor's know that the Cymbalta just isn't cutting it..... Good luck to you..