"I called everyone of the women and told them. It wasn't revenge as much as I felt they should know he was using them."
One man said that he's snooped through every single partner's phone - and has found what he was looking for in every instance.
"They were talking to and flirting with other men, had exes naked photos, and sometimes actually physically cheating," he said.
One woman's worst nightmare was realised when she discovered her boyfriend was cheating on her with her best friend. She explained: "I saw a text from my best friend (at the time) pop up on his screen asking 'have you said anything to her yet?' So while he was pumping gas, I scrolled through his texts. Yep. Ex-bf, ex-best friend."
Another lady found a lot more than she bargained for when scrolling through her partner's iPad, admitting she found Facebook messages from other women, an OK Cupid account and "dirty texts".
"I feel justified in my actions, and I don't care if that makes me a bad person. I knew something wasn't right, so I needed to find out myself," she said.
Speaking to Refinery29, one woman explained that she was left dumbfounded to discover her beau had been googling "mature escorts".
She explained: "I was out on a date at a restaurant that was going pretty well. We decided to take the night on and go to a cocktail bar in Soho. I borrowed his phone to look up the address of a place I liked when I found 'mature escorts Mayfair' in his Google searches. I left pretty soon after that."
A lady was left devastated when she discovered messages from her boyfriend to his ex saying his current relationship didn't match up to his last.
She revealed: "I found Facebook messages between my boyfriend and his ex-girlfriend talking about how much they missed each other and how things just weren't 'the same' with me. I was devastated and left him soon after. I never told him I found those messages and everyone thinks I dumped him. It's a pride thing."