Found: YA thriller wife doesn't recognise husband

The book I'm looking for is fictional and while I remember the plot really well, I do not remember either title, author or cover. I read it about 6-7 years ago I'd guess. I read it in German but assume that it was written English originally. As for the plot: It starts off with a young woman being home alone and suddenly somebody is ringing at the door. She opens and the man tell her that he is her husband, but she does not remember him at all, nor are there any items in the house that would account for him telling the truth. Then the pov changes and it goes something like: Imagine you're coming home and your wife doesn't recognise you anymore. You have been erased from her life. Who is telling the truth? Something along the lines of this is what the blurb says. He then moves in and they try to live as the couple he says they are. She is getting those weird impulses, whenever she has a knife in her hand, to hurt her husba I distinctly remember a scene like that where she then bangs her head involuntarily against the wall instead of acting on the impulse. The books switches between the persepectives (I think) and the reader only finds out at the end who is telling the truth and what has happened to cause the other one to be convinced of the opposite. I know that it was him telling the truth and something about hypnosis that worked on her even though it wasn't directed at her because they used her mothertongue. They made her forget about her husband and planted the impulse to kill him.

I couldn't think of anything else and went into an in depth internet research and I found it! Its a German book called "Fremd" by Ursula Poznanski and Arno Strobel.

touchstone: Fremd

The Silent Patient?