Justin Bieber remains as convinced as he appears hopeful that one-time girlfriend Selena Gomez will soon return to him

HollywoodLife.com reports that even though Bieber is trying to "stay busy with his music," his mind never seems to stray far from Gomez, who is now rumored to be dating DJ Zedd.

The website adds the 21-year-old Gomez is the only girl Bieber insists he would want to be in a "serious relationship with" and considers her the only girl he "would consider marrying."

The 20-year-old Bieber and Gomez have dated off and on in recent years, recently breaking up yet again and moving "Heart Wants What It Wants" singer to apparently take up with Zedd.

"Justin is in complete denial about Selena and Zedd," a source told HollywoodLife. "He thinks she's in a rebound relationship and will eventually come to her senses."

Other media outlets have reported Gomez and Zedd appear to be growing closer and closer and have recently been seen all over the map together as they work on their upcoming collaboration, "I Want You to Know."

"Selena is really excited about her future with Zedd," added another source. "They bond on every level and she's just in the best place ever. She loves that she doesn't have to play down her feelings for Zedd on social media like she had to with Justin."

Bieber recently took to social media to express some of his innermost thoughts about his predicament.

"I didn't want to come off arrogant and conceited, or basically how I've been acting the past year and a half," he said in a YouTube video. "I'm not who I was pretending to be. Often we pretend to be something we're not as a cover up of what we're truly feeling inside. And there was a lot of feelings going on in there."