“my husband told me he’d be happy with or without them, as long as we stayed happily married. At the risk of sounding flaky, I don’t have a good explanation for why I changed my mind about children.”
You probably wisely realized that one day, that husband would knock up that hot new young girl at Starbucks when you hit your control freak stage. The instinct to breed doesn’t vanish for most sane people.
Having or not having children is one of those excellent things to figure out before marriage.