Selena Gomez took Justin Bieber back “with much heartache,” sources exclusively tell Page Six . After their split, followed by his much- publicized flirtation with numerous Victoria’s Secret models earlier this month, sources tell us Selena is “far from happy with how he has treated her.” Spies said Gomez was spotted dining with fellow romantically traumatized singer Taylor Swift at Osteria La Buca in Hollywood on Saturday night. A witness told us, “They shared a few appetizers and one entree. Taylor was overheard giving Selena advice about how to deal with a breakup. Selena looked unhappy.” The following day, Gomez was spotted backstage at the American Music Awards with Bieber, and the pair (left) headed to an after-party at the Marriott Downtown. But the source added, “Things are still pretty volatile between them.”