What Horror Movie Genuinely Keeps You Up At Night?

ok i really don't get scared from horror movies anymore, seeing as I've been watching them since i was a kid. i need some great scary movie recs that will genuinely terrify me.

if theres gore, thats fine, but i don't want a movie that uses pure gore as its' "scare factor".

seriously...gimme something that makes you lose sleep and has never left ur head since the first time you watched it :)