Kristen Stewart reportedly admitted that she was prompted to cheat due to "her own insecurities".

The actress recently publicly apologised for cheating on her beau Robert Pattinson with her Snow White and the Huntsman director Rupert Sanders.

Robert has several friendships with gorgeous high-profile celebrities such as singer Katy Perry and his Remember Me co-star Emilie de Ravin.

Kristen is said to have been extremely jealous of his tightknit relationships with other women.

"Kristen's admitted her own insecurities may have pushed her to cheat," a source told the US edition of OK! magazine.

Robert is struggling with his own anxieties, as the actor is reportedly awake at night wondering if Kristen made other transgressions during their relationship.

"He totally trusted her, so this has really rocked his world," the insider explained. "Rob's now started to question everything. He's looking back at all of the other men in her life and wondering who she might have been with.

"She swore Rupert was her only mistake, but Rob just doesn't believe her. He's going nuts trying to come to terms with all this."