The Britain's Got Talent judge was left in a critical condition during the Caesarean section delivery of her little girl Hollie in 2012.
The problems began during the birth when doctors discovered that her placenta was attached to her internal scar from her previous Caesarean section.
The doctors then attempted to pull out the placenta, not realising it was attached to her bladder and the actress, who has a history of difficult pregnancies, lost a huge amount of blood.
Speaking to The Sun On Sunday, Amanda, 43, said: "As much blood as they were putting in me was going out. It just would not clot. For seven minutes Chris didn’t know if I was alive or dead."
"They literally ran out of my blood group in London. They had them on mopeds coming from everywhere with it.
"There was a moment where they said I had flat-lined for 40 seconds. My heart stopped and I was literally moments from death. It was touch and go."
Amanda's heart stopped beating for 40 seconds, but, thankfully, doctors were able to save her life.
However Amanda has now admitted that, despite making a full recovery, the stress of the episode let to her being diagnosed with PTSD (post-traumatic stress disorder) - a condition which is often associated with war veterans.
Speaking with Radio Times magazine, she said: "After that, I thought seriously about illness and assumed whenever I had a cough, it was lung cancer.
"I've had therapy and was told I suffered from post-traumatic stress syndrome... I assumed that (Ptsd) was what people had in Afghanistan, and I haven't fought a war, but maybe I have in a way."
As well as little Hollie, Amanda has an older daughter, eight-year-old Lexi, but also suffered a miscarriage in 2010 and then had a stillborn son, Theo, a year later.