I smoked when I was pregnant with both James and Madeleine.... I hated it, and wanted to quit soooooo bad, I just couldn't do it.
I cut down on the milligrams, and how many I had per day... I smoked around 2-3 per day, and made sure I only smoked when I was desperate. Some days I didn't smoke at all.
When I fell pregnant with Noah, I gave up smoking... I stopped on the day after my wedding... I was 7 weeks pregnant.
I smoked again for a month after losing Noah... I decided that it made me feel gross, and it was best for me to stop so I could give my body the best chances for TTC.
I haven't smoked now since March 2006... just over a year.

I wish you all the best... quitting is hard... and I think you definitely need to have a supportive partner... My DH doesn't smoke, but never pestered me to stop... he encouraged me when I did. Also, don't beat yourself up if you do have a smoke, it is hard and you don't need to be hard on yourself too.

My biggest thing was being able to say how many days I haven't smoked for... If I had gone a whole day, then I could say I haven't smoked for a day, or a week or whatever... if I had one, then I had to start that all over again.