Thanks for this. Y'know, I wish the people around me thought the same way that you think about this. It seems largely unthinkable to people that I would be reconsidering this now, after marriage, and I've been almost shamed for it. And I know it's not ideal, for sure. I wish I would have had these weird feelings crop up even a few months sooner than they did. But I am where I am, and the only thing I can do is move forward; no use in expending energy on how the past could have been.
I've had enough conversations with female friends in their early to mid 30s who have never wanted children and have suddenly found themselves changing their mind about it. Although I decided at a young age that I didn't want children, it wasn't until I was in my late 30s and seeing the effects that having children had on the way some of my friends were living their lives that I felt absolutely sure about the decision.
I think that what makes the decision somewhat more tricky for women is that age really does matter. Men are not making the same unchangeable decision - and I have several male friends who became fathers in their 50s something that is almost always impossible for a woman to do.
So it seems to me that for women, 30s is often a decade of great deliberating and thought and mind changing on the subject of children. Whatever you decide will shape the rest of your life so it does need lots of thought.