When someone is gaslighting you, it means that they are doing things that cause you to end up questioning your own sanity. The term came from the film Gaslight, which was based off a play from the 1930's. In the film, the main character's husband is narcissistic. He manipulates her until she thinks that she is going insane. For example, he's causing the gas lamps in the house to dim or brighten, but tells her that she's just imagining the changing light