I don't usually do this, but I'm trying to find the story where the baby refuses to come out and ends up maturing inside and ends up pregnant herself inside her mom, and the cycle continues... I wish I could remember even where I've seen it as that would've helped my searching.

This one?
https://preggophilia.com/iris-t

I remember reading that story like 3 years ago, thinking "damn, this is great!"

That must be it! I feel like there's some plot points I remember that are missing, but I may be confusing it with other stories because it definitely sounds pretty darn close to what I was remembering. Thanks!