Tulisa Contostavlos has told how she became a "ghetto Miss Marple" as she tried to discover whether boyfriend Fazer was cheating on her.
The X Factor judge said she had suspicions about Fazer, her boyfriend and N-Dubz bandmate, and already found it difficult to trust men after she caught her former fiance, Adam Bailey, cheating on her.
In her new autobiography, serialised in The Sun, she tells how she started checking up on Fazer before finally calling time on their two-year relationship.
She said that she'd demand to check his phone after the 2011 Saturday night X Factor show, to see if there were any messages from girls, and even tricked one girl who was sending flirty texts into sending them to her instead.
After she finished filming the ITV1 show, the couple were about to go on holiday to the Maldives, but Tulisa heard rumours that Fazer had taken a girl back to their house.
She said she was like some sort of "ghetto Miss Marple, scouring Facebook" trying to find the woman - but that a friend of the woman said she was obsessed with Fazer and had probably made it up.
But on holiday, she decided enough was enough and she couldn't take the paranoia and jealousy any more.
Tulisa said she had no proof that Fazer ever cheated on her, but when he refused to take a lie detector test, she decided to finally call it a day, writing in the book Honest, My Story So Far: "There has to be a point when self-respect takes over, and this was it."