"So Yeah -- Of Course I Told Him YES. Anyway, It Will Mean That I'll Be Spending About A Week With Him

"So yeah -- of course I told him YES. Anyway, it will mean that I'll be spending about a week with him every month -- during my fertile time -- and he said that he would only help out like that if I promised to not have any sex with you at all until after he's impregnated me. That's OK with you, isn't it?"

You're not sure how you really feel about this, but it's obvious that it's what your wife REALLY wants, and you also know that once she makes up her mind about something, there is essentially zero chance that she'll change it, so you do the only thing you really can do at this point, which is to pretend to be in complete agreement with her.