Testing in PA?

I am 20 weeks now, and I have been to every OB appointment, and no one has drug tested me, or if they have I was not told about it, though I'm sure it would have been positive since I have continued to smoke throughout my entire pregnancy. 

It never occurred to me that if I had tested positive they might have just made a note of it for when I give birth rather than talking to me about it, but I've read that may be the case. It seems very dirty and underhanded. I am a grown, successful woman and I have no history of drug abuse. There would be no suspicion to test me, unless of course they tested me previously and just kept that to themselves. 

My second question would be, how far from birth would I need to stop completely for baby to not test positive. I'm not worried about my own pee, but I know he's been working on his first poop for a few weeks now, and I have smoked several times during that period, is it too late for me to stop now?

I am so disappointed that this herb that I don't feel is causing any harm to me or baby is now leading to so much stress and fear that I could lose him 😔