be on somebody's back
be on (one's) back
To be constantly nagging one about something. Ugh, my mom is on my back all the time about my grades, but I just have no interest in the classes I'm taking this semester.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
be on somebody’s ˈback(informal) annoy or criticize somebody a lot: My new boss is on my back all the time, saying I have to work harder.
Farlex Partner Idioms Dictionary © Farlex 2017