I find myself in this situation, where I did let my WAW come back to easily.
From D-Day in December to March, I was chasing her. She went from a loving wife and caring mother to acting like a teenager, spending entire weekends, even sleep overs during weekdays, with the OM. She talked about separation, she wasn't happy, basically followed the script.
When I did the 180 at the end of Feb, she was the one who asked me if we can still work it out and of course I said yes.
I told her she has to go NC with OM, but she hasn't been serious about it. She said something like baby steps. She stays at home now, doing more work around the house, talking about future vacations, but I know she's still texting and possibly seeing OM during the weekdays.
We're friendly at home, even sweet, so I'm really confused how to handle this situation. She does ask for my attention and affection, something that was lacking pre A. I fear that when I go strict on her like a parent, it will turn her off and run back to the OM.
How can I make her "go thru pregnancy" as you put it, without her leaving again?