I did not watch Breathless, but the feeling you describe reminds me of what I experienced watching La Piel Que Habito by Pedro Amlodóvar (a loose adaptation of a novel: Mygale by Thierry Jonquet).

It was an incredibly difficult movie for me to watch, the amount of psychological violence was so unbearable I barely made it to the end, couldn't help but think what could possibly go through the mind of the writer to give birth to such a twisted story.

(Note that Breathless has Godard for direction and screenplay but the story is Truffaut and Chabrol)