Selena Gomez has got to be crying her eyes out right now and texting Bieber NON-STOP!  

The Biebs posted this throwback pic Sunday night and then DELETED IT!  Ugh, just when Selena thought there was a ray of hope, he pulled the rug out from under her!

After a whirlwind trip to St. Maarten and then on to Paris, the on-again-off-again couple's relationship seems to be OFF again, after Bieber lunched with Kendall in the City of Lights on Tuesday AND partied with Kendall and Gigi Hadid at the Carine Roitfeld party on Wednesday ... while Selena was still there!

Of course Selena jetted her butt back to LA to find solice in her sofa and a bucket of Ben & Jerry's, while Justin's off on his private jet -- in Greece, we're told.

What is Justin trying to do to poor Selena, posting and deleting a photo like this???!!!  Ahhh, young love ...