Robin Thicke Pours out his Heart on Stage - 'I'm Lost without Paula'

Awwww, Robin knows he's messed up big time and he's now doing all he can to win his woman back. According to TMZ, Robin Thicke got back to performing last night and wasted no time using the stage to beg for Paula Patton's mercy ... opening up to the crowd about their break-up and dedicating a song to her.

They are officially separated but Thicke wore his wedding ring through the show in Fairfax, VA and told the crowd:

"For y'all that don't know me and my wife separated, but I'm trying to get my girl back. She's a good woman." He also told fans he'd written the song "Lost Without U" for Paula ... before launching into the hit -- which we gotta say is kinda the perfect song for a guy trying to get back on a chick's good side.

Then again, Paula's heard this tune a hundred times. Would you take Robin back if you were in Paula's shoes?