Not a doctor here, but personally I would be concerned about taking Duloxetine (Cymbalta) and Nortriptyline together esp. since you're taking a high dose of the Cymbalta.

Then there is the codeine added as well.

Did the same doctor order the Nortriptyline and Cymbalta together or separate doctors?

Check out a drug/drug interactions checker like this one
http://www.drugs.com/drug_interactions.html