Bummer. Do you mean starting with step 624? That might be a problem, because it requires giving Janice a sleeping pill which I can't seem to do now she's pregnant.
You shouldn't need to, if you've done the mom swap previously, all you'll need to do is speak with Billy at school and ask him to do a mom swap.
But, uf she's pregnant, you'll have to wait till she gives birth before you can do it.
Her being pregnant disables certain options.
If you want to save time, I recommend downloading my 0.35 save and restart the 0.36 section of the walkthrough.