Can a beta male get impregnate???

Yes.

Yes. In this story, yes.

Thank u....I was a little confused

The way it is explained is vague. Through the flashbacks we can see both boys are considered to have fertility issues, but still, even though Kudo tells Miyauchi that, if push comes to shove he will bear the child. But in the end, Miyauchi is the one who gets pregnant with Yuuichi (only the most adorable baby in yaoiland!)

I think only Miyauchi has fertility issues, though? The doctor says they might come from the time when he was a neglected kid - his development into an adult may have had some problems. Kudo is reluctant to bear the child, probably partly because he's "straight" (has previously only liked women) and because he has some traumas from the time he was r*ped.