be on somebody's case

be on (one's) case

To be constantly nagging, harassing, or annoying someone. My boss has been on my case all week to get that report done. I'm sorry for being on your case about it, but I need an answer soon.
See also: case, on

be on somebody’s ˈcase

(informal) criticize somebody all the time: She’s always on my case about cleaning my room.
See also: case, on