I just had a thought---you could talk to a separate nurse/doctor/midwife about this before to long and get their advice/ reassurance off the record, and then talk to your Doc when you're comfortable.
P.S, I have a friend that was addicted to Morphine, and he has a terrible leg condition that he's in chronic pain for, and they give him....morphine. So, go figure.
In any case, pain meds are not your only option. An epidural is a med free way to cease the pain if need be.
Good luck!