Get Used To The Real World - Kiribaku Mpreg
And they thought high school was scary.
Eijirou got badly injured in a villain fight. Katsuki was pregnant and working at UA, with no way to help him. Obviously Katsuki doesn't want to think about the fact that he could become a single father of four any day because of Eijirou's condition.
Definitely scarier than high school.
Sequel to 'Get Used To Waking Up At Four AM'