"this baby came out of you but im not 100% sure its yours"
NO LISTEN, THIS IS LEGITIMATELY SOMETHING THAT HAS HAPPENED.
Check out Lydia Fairchild.
While applying for government assistance during her third pregnancy, a DNA test to confirm that her separated husband was indeed the father of the children, it was discovered that Lydia was not, genetically, the mother — despite having given birth to them and hospital recording proving such. This resulted in big nightmare with the kids being taken away and the family having to fight for it, because the court completely dismissed the hospital records. When Lydia gave birth to her third child, that baby was also found to be genetically different from her.
Finally, it was discovered that Lydia was a Chimera; a person composed of genetically distinct cells. Specifically, her ovaries were, at the genetic level, from the twin sister she absorbed in the womb. She had essentially conceived and given birth to her biological nephews.
So yes, while unlikely, it is possible to give birth to a child, be witnessed giving birth, and still be challenged on whether or not they’re yours.
(sidenote; in addition to the family being poor, the father of the children was black and the mother white, so those were likely big factors behind it turning into a court case instead of a medical novelty as with the loosely similar case of Karen Keegan.)