Do you know what kind of bug this is?

pleaseeee help, okay so at my boyfriends theres these bugs that keep gettting in, they are black and skinny with long antennae, they vary from size but they fly sometimes (but mostly just chill on the wall) they freak me out, i have looked online and cant find anything about them.. ALSO when you try to killl them you have to hit them like five times really hard.. does anyone know what these are called?