on your tail

on (one's) tail

Following or pursuing very close behind someone. The cops are on our tail—we have to lose them in the woods. Why is this guy sitting on my tail when I'm already going over the speed limit?
See also: on, tail

on your tail

COMMON If someone is on your tail, they are following you closely or are chasing you and trying to catch you. He entered the finishing lap of the race with Piper right on his tail. He heard the wail of police sirens, loud and close by. They must be on his tail at last.
See also: on, tail