I don't really know how to reply to your question about "Who's your Daddy"
But question one:
Some people can be different when pregnant. It just depends on the body you know ? They'll be a slight tiny pudge or some people will show a belly early on during the pregnancy.
[Ive read two books were they looked skinny af]
Question two:
Mpregs or omegaverse world depending on the author really. They'll either have a C section operation or they will give birth outta the ass..I've read two where they'll give birth through the ass. But the rest have been a C section operation.
Question three:
You can have sex while pregnant. Sometimes if you are trying to get that baby outta there doctors will recommend sex.
It's a mpreg just another fanfiction like how there's furry fans you know?
Hopefully this helped ~
I'm glad denji could have a happy life in another universe, even if he had to get pregnant
THIS IS CRACKING ME UP BRO