be on someone'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.
See also: back, on
Farlex Dictionary of Idioms.

be on (or get off) someone's back

nag (or stop nagging) someone. informal
See also: back, on
Farlex Partner Idioms Dictionary
See also:
  • be on (one's) back
  • be on somebody's back
  • back at it
  • back at it (again)
  • back onto
  • back onto (something)
  • a fire extinguisher
  • (a body part) is killing (one)
  • a thing
  • a whole thing