Firstly I'm going to say I'm a non smoker so can't relate to how hard it must be so I wish u so much luck and success.
Secondly - as a student midwife in my final year of a four year degree here in Nz I want to say some things that I learnt recently I'm a smoke change workshop that may or may not help one thing I remember clearly is that some ppl swore by being asked if they would give their baby that smoke to hold, or blow their smoke in their babies face? Not as a 'u should feel guilty tactic' but more of a way of imaging it to try curb cravings another piece of advice given was make changes u can make. Cut down to a certain number, try skipping a smoke at a certain time, flicking coffee if that makes u crave one. Replace 'smoking time' with a walk, a milkshake, just something else we learnt also that if u stop smoking before 15 wks all effects are reversed by birth effects to placenta and to babies oxygen intake etc so I know u are 21 wks so just think u would still be more than likely able to reverse any effects or reduce them loads.
As I said - I'm a non smoker so to me these things sound 'helpful' but I don't have that same addiction so can't really know xxx
I also have some solid information relating to cot death risks if that would help u imagine how it happens etc? That's kinda scary so don't wanna bombard unless u want another thing that may or may not wk!
Hope I haven't offended, just practicing techniques and info we just have been trained on.
I'm sure you will do it