You weren't raised conventionally.
Growing up, you don't remember much about true love between your parents, only fights that ended up too heated for you liking, with insults thrown around and maybe a few plates as well.
Still, you liked Katsuki, a lot. And he liked you too, surprisingly.
You were a bit weary when you both started dating, which he assumed was only because it was a new thing for both of you, and mostly thought you just needed time to feel fully comfortable. But he kept his attention on you, and if you thought you could fool him, you were dead wrong.
He didn't liked the way you always seemed to be walking on eggshells around him. He was your boyfriend, wasn't he? Why didn't you trusted him?
It seemed like you were just waiting for something to snap or for the worse, and it was starting to frustrate and piss him off on equal parts.
He didn't knew how long he could stay quiet about it without confronting you.