The Loose Women star was pushed to breaking point following the arrival of daughter Amy, suffering an umbilical hernia and contracting MRSA when she underwent a procedure to correct it.
"I felt like a shadow had passed over me and I could still feel its terrible chill," she revealed in her book Confessions Of A Good Girl, serialised in The Mirror.
"Yes, it was an over-dramatic reaction but it sent me into a tailspin and then a frenzy of sorting out wills and life insurance. My mortality and fragility shocked me. It was one of my lowest points.
"Mentally, I had not returned to my normal happy self after having Amy, something I denied for a long time - until the blackness became too big to cover with a smile."
McLean - who also has 10-year-old son Finlay from her first marriage - only chose to seek help after mentioning to second husband Steve Toms that she felt the family would be better off without her.
"Steve was livid," she recalled. "'What a stupid thing to say!' he snapped, jumping out of bed. 'I won't have you saying things like that. Just sort yourself out and deal with it.'
"[The doctor] told me it wasn't failure or weakness but something many women went through after having babies because of hormonal imbalance. She smiled and said that it was a wonder I had coped for so long and she gave me some tablets that changed everything.
"I didn't go from tears one day to bouncing about the next. I just began to feel normal... I'm not ashamed anymore that I need help to cope, because you know what? Life is hard, and sometimes we all need something to help us get through."
McLean revealed yesterday that she is to divorce Toms after two years of marriage.
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