And in Facebook posts she made last night and this morning, it seems Katie may have already been aware of her husband's cheating, hours before she announced the news to her followers.
Sharing a quote from dailypositivequote yesterday afternoon, Katie posted: 'Don't worry about hard times because some of the most beautiful things we have in life come from changes and mistakes.'
And a few hours later, Katie shared a picture with the quote: 'Don't put the key to your happiness in someone else's pocket' suggesting all was not well in her romantic life.
'Don't put the key to your happiness in someone else's pocket'
This morning, Katie added the quote 'Day Three: I declare I have the grace I need for today. I am full of power, strength, and determination. Nothing I face will be too much for me. I will overcome every obstacle, outlast every challenge, and come through every difficulty better off than I was before. This is my declaration.'
The mother-of-four announced just days ago that she is six months pregnant with husband Kieran Hayler's child.
But in a shock tweet this morning, Katie revealed that her and her husband would be divorcing after she discovered he had been having an affair with her best friend, Jane Pountney.
She continued: 'Jane Pountney is 50 next year cloned into me with my help she is a w****, home wrecker s***.'
'Kieran is a disgusting human being doing this after I've just had a baby and still doing it till I caught them.'
'No human being deserves this especially being 6 months pregnant.'
'Worse pain in the world,' she added.