OK, to answer some questions honestly.
Why when you can see your baby bump and feel it kick do you still choose to light they cigarette and inhale its smoke? Why don't you use the early weeks to acutely address it. Or even before you fall pregnant?
Well, as I said before not everyone is actively trying TTC and an unexpected pregnancy can take a long time to feel real. That is how it was for me. I didn't feel pregnant for a long, long time. All I had was a piece of plastic that told me I was apparently pregnant and what felt like the world's worst case of food poisoning, which ironically made me want to smoke more (for comfort). Even at the 12w scan I don't think I really, consciously grasped that I was pg, in some weird way.
And then suddenly I was heavily pg and still having the odd cigarette and that felt so much worse that as other posters have said, it seemed so much harder to admit to anyone that I hadn't knocked it on the head in the first few weeks. And because it felt harder to admit, I felt guiltier, and I got stuck in a vicious circle.
Also, I think the concept people have of seeing that pink line on a stick and immediately feeling an overwhelming protection to the life inside of you is in some ways projecting a very personal interpretation of pregnancy onto everyone else's experience of pregnancy. As I said, that wasn't my experience of pregnancy. Hopefully it will be next time around, but it really wasn't my experience with DD1. There was so much else going on in my life that I swear I was waddling and having an elbow in my lungs before I really connected with the baby inside me.
Yes I am naive to the intricacies of addiction
To me, that is the crux of it. If you have been fortunate never to have been addicted to something in your life then it is very hard, as much as you may try, to understand why rational and logic and reasonableness doesn't just win out. It is hard then to understand what I've tried to explain about about guilt and shame and stress and using that addiction as a stress relief.