If it works, is he actually considering keeping you on Codeine until this resolves (which may be years)?? That's really unusual to start with a narcotic and to go with more likely drugs that will help, second. Not sure how much he Rx'd for you, but large or frequent doses of Tylenol are horrible for your liver.

At least you will know if narcotics will help, though. but I wouldn't stay with that if it helps...you should still try other options first.