For the most part, opiates have little known effect on pregnancy. There IS a risk of miscarriage from oxazepam, by the way-- so that drug is not to be taken in the first trimester. But even the issue of withdrawal in newborns is overblown; I have seen the same nurses who 'tsk tsk' an opiate-addicted mother help to hold down the arms and legs of a newborn so that the circumcision can be performed-- without anesthesia. Not to mention what it feels like to have your head squeezed to half the normal size during the birth process-- that can't feel good!!
Give yourself a break; the important thing now is to do the 'next right thing'-- now that you know your weakness for opiates, your job is to keep yourself as far from them as possible. Keep them out of your house whenever possible; consider telling your doc about your 'opiate issue' so that in the future you are given the least addictive options.
Good luck with the baby-- the opiates are not an issue at this point-- try to keep them from being an issue in the future.
I think your baby will be fine. Just don't take anymore unless you're in severe pain. My teeth suddenly went "bad" during my 3rd pregnancy and I had to take tylenol 3's a few times. But I was on 50 mgs zoloft daily and oxazapam as needed (like every 6 weeks or so) and my baby turned out very healthy and is in perfect health now. I was scared of her having withdrawals too so I breastfed her for a year, I don't know if that's proven to work but she was a very calm and smiley infant. Just don't worry-- if the Dr.s gave you the medication they must think it's safe. take care!