The 40-year-old beauty split from the former stripper - the father of her youngest children, Jett, four, and three-year-old Bunny - earlier this year after four years of marriage and she claims she discovered he'd been unfaithful after checking his phone while he slept.
She said: ''The truth is, I caught him cheating again - this time with a 19 year old who works in the Co-op.
''And he's been texting an ex. I've got all the messages - I needed to see them to finally know what a lost cause he is.
''He kept accusing me of stuff and it was annoying me because I knew he was probably cheating. Anyway, one night when he was asleep, I got his finger and pressed it against his phone so it unlocked it, and there it all was. It was all there.''
And the 'Loose Women' panellist admitted she feels like she's ''wasted'' the last five years of her life because she should never have reconciled with Kieran after they previously split when he had an affair with her friend Jane Pountney.
She told the new issue of OK! magazine: ''He'll never change and I just can't stand him. I should have split up with him when he first cheated on me but I was so determined to make it work.
''Right now, I feel like I've wasted five years of my life with him.''
Katie - who also has three other children, Harvey, 16, Junior, 13, and 10-year-old Princess, from past relationships - has moved on from Kieran and is now dating Kris Boyson, even though she wasn't looking for a new relationship and says he's like no one she's ever been involved with.
She said: ''So I did actually want to stay single, but I randomly met him through Harvey. Kris is a weight loss specialist and he was working with Harvey on a new programme.
''I've never had anyone who's like him - he's a man's man. He's got his own job, he's not false or fame hungry. He goes to work and doesn't want to hang around me at work. In that respect, I think this is going to be a more normal relationship and less toxic. We'll have our own space.
''He's been slated in the press and he's just not that person. He did those [reality] shows ages ago because people said it would help boost his profile as a trainer, but he's not fame hungry at all. He's an absolute grafter. He's a gentleman and it feels like he's the first one I've had in my life.
''He does actually tick all the boxes!''
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