The 19-year-old has hit the headlines during his stay in London, including being two hours late to one of his gigs, wearing a gas mask in public and getting into a scuffle with a photographer.
Sources close to the star claim that he has struggled without Gomez's presence in his life.
"He was crazily in love with her. She kept him grounded," an insider told The Sunday People.
"She's been a tower of strength through all the hysteria of being one of the world's most famous popstars. To lose her was like losing an anchor."
They continued: "He simply hasn't been the same since he split from Selena. It really broke him.
"They were together for such a long time for two people so young. He hasn't quite known what to do without her. He is lonely.
"They kept one another very grounded and understood the level of fame that they both had. Now his friends know that he needs their support more than ever."
Bieber and Gomez split after a two-year relationship during a New Year holiday in Mexico.
Meanwhile, Bieber's friendship with rappers Lil Twist and Lil Za has also been blamed for his recent antics.
"You have to look at the people he is hanging out with," a Hollywood insider told the Daily Mail.
"They are very distinct from the group of professionals around him, like his manager, who do a terrific job guiding his career and caring for him. Justin's issues really started when he started hanging out with this undesirable crowd."
Bieber has thanked Will Smith for his "great advice" during his recent troubled times.