Paula Patton -- Robin Thicke Won't Get Me Back by Crying

Robin Thicke can cry all he wants on stage about his love for Paula Patton ... but it's not going to change her mind about leaving him ... sources tell TMZ. For that ... he has to do something else.

Sources connected with the couple tell us ... Paula is unimpressed with Robin telling both TMZ and thousands of concertgoers he's trying to win her back.

Here's the good news for Robin. Although she TOLD him she wanted a divorce, she hasn't hired a divorce lawyer yet and she's open to reconciliation.

BUT ... before she takes him back, Robin has to prove his loyalty to her ... by his actions. She's keeping tabs on him at his concerts, watching who he hangs with, which parties he attends -- especially the after parties -- and what photos surface.

We're told Paula knows photogs have their cameras trained on Robin, and she views the paparazzi are her private detectives.