No break up is ever easy ... and Justin Bieber can attest to that. Since splitting from Selena Gomez, the "Baby" singer has found himself at the center of some pretty scandalous cheating allegations ... and he's speaking up about it.

On Friday Bieber took to Twitter to let fans know what he thinks of the stories circulating.

Justin Bieber's tweet came after Star Magazine published a story of the alleged "real" reason behind his split from Selena Gomez. According to Star, the singer was "stoned" and "engaged in sexual activity with a 22-year-old nursing student" named Mimi.

The alleged sexual activity occurred on Dec. 21 at the Beverly Hills Four Seasons hotel. An insider told the magazine that Bieber, his rapper buddy Lil Twist and Mimi "all went to buy weed at a smoke shop on Olympic Blvd. in Hollywood, then they got food at McDonald's and went back to the hotel."

By the end of the night Bieber allegedly moved the party into his bedroom suite and started busting some moves on Mimi. The insider told Star that, "Justin surprised her by saying, 'I want to know if you taste good.' He started kissing her cheek and her ear and neck and then her whole body."

Bieber reportedly kept his clothes, but stripped Mimi of hers for a "marathon session."

Selena Gomez has turned to friend Taylor Swift since her split from Bieber.

"We have both experienced the same things at the same time ... But we've never once talked about our industry," the Daily Mail reports Gomez saying about Swift. "She just became the person I'd go to for an issue with my family or boyfriend."

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