From Longman Dictionary of Contemporary Englishbe on somebody’s backbe on somebody’s backspokenFORCE somebody TO DO something to be trying to make someone do something they do not want to do Why are you and Dad always on my back? → back
Examples from the Corpus
be on somebody’s back• Aunt Mimi was always on his back about him "wasting time playing that silly guitar".• Nick knew that the coach would be on his back if he missed another training session.• He must be on his way back by now.• His father was on his back night and day.• By this time the Confederates had formed into columns and were on the march back to Corinth, Mississippi.• Seeing that stately building on a hill and knowing the respirator center was on the back with the water view heartened me.• The boss has been on my back about that report.• Their other project, meanwhile, is on the back burner.• The afternoon papers are on the back seat and he reads them until the limousine stops in front of a funeral home.• Her eyes opened; she was on her back.• Instead of automated leisure, enforced unemployment was on its way back. 