The former glamour model and mum-of-five made the emotional admission on an episode of ITV's Loose Women, saying 'I've been married three times and they've all been different kind of marriages. One was abroad, one was in Vegas, and then with Pete it was where Downton Abbey was filmed, Highclere.'
'So we got married there but I had really bad postnatal depression and not anyone knew that there so it's sort of, kind of, a blur and I wasn't on antidepressants.'
'So I remember bits of the wedding but it's I wish, no I don't wish I could go back and do it all over again, but you know, it was such an amazing wedding. You know, everything about the fairytale that I wanted, but I had postnatal depression.'
Katie talked about her struggle with postnatal depression as part of Loose Women's 'Love Week'
Katie and Peter were married for four years, from 2005 to 2009, and had two children, Junior and Princess, together.
Her revelation on television is not the first time she's detailed her difficulties after Junior's birth.
'My depression got so bad that I actually turned to drugs,' she told OK! magazine in 2010. 'I was desperate to get out of my head. After I took it I thought this feels good.'
'Suddenly I started to feel really strange, my heart seemed to be racing fast. In bed, sleep was out of the question as I lay there wide awake, tormenting myself with thoughts, convinced I was going to die.'
'Shortly afterwards, I considered killing myself after Peter threatened to leave when I told him I'd taken a drug.'
Katie and Peter were married for four years after meeting on reality show 'I'm a Celebrity, Get Me Out of Here'
She added that she'd even considered driving herself into a wall, but realised she needed to be pull through for the sake of her family.
'Eventually, I had to spend some time at the Priory. I went along to speak to the doctor there. I got everything off my chest.'
Postnatal depression is common, affecting around 1 in 10 women in the UK after having a baby - it can develop within six weeks of birth, but is often not recognisable until around six months afterwards. Symptoms vary from person to person, but often include extreme low mood, and feeling unable to cope.
If you think you may have postnatal depression, there is help available. Visit nhs.uk or speak to your doctor to find out the options available.