It also could be hormonal change too. Pregnancy can cause hormones to influxes which change people behavior. The person could show symptoms like crying more easily, get mad, or overthink on little things (which Mc showcase a lot through these pass chapter) I think the author really show the realistic aspect of pregnancy.
I was thinking the same thing. She must be having a hard time since she’s stressing over revenge and have a lot to do so the fact that she doesn’t have a lot of control over her emotions anymore bce of her hormones from the pregnancy isn’t surprising. She’s been suppressing a lot of her emotions to begin with, but I assume she’ll tell him after everything is over.
I just don't think he would react negatively if you told him you might be pregnant. Is it a stressful time? Yes, but I'm sure knowing he's having a child with you is not a bad thing in his mind. However, it's understandable why she's not thinking that way. She's focused on revengance and clouded with fear and doubt right now.