This is most likely Blood Curses and Malfoys by Nebel Engel
"Do you think you are the only one with problems, Granger?" Draco
stood in front of her, anger written all over his face. DMHG Set after
Voldermort's defeat, Hermione and Draco must face an arranged
marriage, their families, and each other. Rated: Fiction T - English -
Drama/Romance - ...
This is Blood, Tears and Drowning Fears.
Hermione asks Draco what he's afraid of...
"You're right," Hermione finally said, fighting to keep her voice
steady although undisguised hurt glistened in her eyes. "What the hell
do I see in you? You're not even vaguely human, Malfoy, because humans
have feelings and you obviously lack that. Humans feel ...
I was looking for it too for a very long time, and I found it (by accident).
It's called "Victim of the Fall" (adult fanfiction site).
I was reading the first few chapters without realising that it was the one i was looking for. It takes a few chapters to get to the Hogwarts part and the new teacher.
As to the other alternative, I have found ...