when he was with HYDRA, Bucky wasn't supposed to want/not want, like/dislike things. So if he showed any signs of wanting/not wanting something, they'd do the opposite. Eventually he figured out that meant if he pretended not to want things he did want, they would give them to him (e.g. he wants human contact so he pretends to flinch away when someone grabs his shoulder and that makes them hold on tighter), and if he pretended to want things he didn't want (e.g. rape), then they won't draw it out as long.
And then he gets out, and he's still stuck in this act-opposite-of-what-you-want mindset and there is confusion and angst and most likely more trash (obviously).