prey on (one's) mind
To cause one a lot of worry, concern, or anxiety, especially for a long period of time. I know that money issues have been preying on his mind ever since the company began issuing pay cuts. I really acted like a jerk on Friday night, and it's been preying on my mind all weekend long.
ˌprey on somebody’s ˈmind
(also ˌplay on somebody’s ˈmind) worry or trouble somebody very much: The death of his father is really preying on his mind at the moment. He thinks it was his fault.The question of whether to accept the new job and move to Scotland had been playing on his mind for days.