prey on sb's mind

prey on sb's mind and
weigh on sb's mind
(to make someone worry continuously; to be in a person's thoughts; to be bothering someone's thinking; think about something and worry about it a lot) — мучить, угнетать, тяготить кого-л.; не давать покоя; не отпускать, терзать, преследовать, следовать неотступно и т. д. {о чем-л. неотвязном, постоянно всплывающем в голове, памяти — мысли, воспоминании, образе, проблеме и т. п.}

Example 1: She didn't reach any agreement with Josh and it's been preying on her mind ever since. — Они с Джошем ни к чему ни пришли, и это не дает ей покоя.

Example 2: I lost my temper with her the other day and it's been preying on my mind ever since. (thefreedictionary.com)

Example 3: The accident has been weighing on my mind all week/ for many days now.

Example 4: I hate to have things weighing on my mind. I can't sleep when I'm worried.

to haunt sb or to haunt sb's mind (to make someone feel worried and upset for a long time; to cause (someone) to worry or feel anxiety because of being thought about too often)

Example 1: Sabina was haunted by a fear of cancer.

Example 2: Dark, spicy marinated lamb, beautiful steaks with homemade green-tomato pickles, the new paprika chicken, so delicate, so wickedly rich with cream—they haunted my mind until I wished to be a boy again, at home on the farm with my family, eating my little head off. (Saturday Evening Post)

Example 3: Thirty years after the fire he is still haunted by images of death and destruction.

Example 4: Images from the war / His experiences in Vietnam still haunt him.
Example 5: Fighting in Vietnam was an experience that would haunt him for the rest of his life.

Related vocabulary:
weigh on sb's mind

[одно на уме]
[on the forefront of one's mind]
крутиться в голове