Check out some foreign stuff, Japanese horror can get pretty creepy.
Also there's a manga titled Fuan no Tane(and Fuan no Tane plus) that is a bunch of short little tales that is best read at night. A lot of them are just creepy and nothing is really explained in them but some of the faces and ideas in those stories will just...you know what just read through it at night. In the dark. With no background noise, for me my mind began to wander with each story I read and the back of my neck started to feel funny and when I left the computer my mind kept thinking about the stories. Had to watch some cartoons to get my mind off it
. Not all of the stories are great but just keep reading them until you finish, each story is unrelated to each other and they're all like 3 or 4 pages long.
But that sounds like what you want, the type of real horror that will make you keep thinking about it. The kind of horror that has your imagination running wild when you're walking down a dark street at night or even when you're walking from the computer to your room in the dark. The kind of horror that follows you before you go to sleep at night, the kind of horror that makes you want to turn on the lights, the kind of horror that makes you constantly keep looking behind you, the kind of horror that makes you afraid to walk into a dark room in your house even though you know nothing is in there but your mind is tricking you into believing that you should be scared.