I'm not a smoker or drinker but I saw a naturopath after my last 2 m/c and she suggested 4 months of taking the supplements she gave me, 4 months of no drinking caffeine and staying away from harsh chemicals (apparently chemicals like cleaning products etc can affect egg quality) etc because it can take that long for new eggs to start to develop I think. I'm not completely sure how accurate this is so perhaps go and see your GP.
I would suggest to quit now, get some pregnancy supplements and maybe start eating a healthy diet for a few months first.
Hope all goes well