"I felt like a failure." Kate Miller-Heidke on her difficult start to motherhood.

“I ended up with a kind of childbirth that 100 years ago, or even 50 years ago, would’ve killed me and the baby, and that knowledge haunted me.”

For singer Kate Miller-Heidke, giving birth to her first son was far from seamless. But it was the months following that plunged her into darkness, feeling like a failure of a mother, riddled with self-doubt and neurosis.

On Monday night’s Australian Story, the Eurovision contestant spoke about her difficult pregnancy, and a side of motherhood rarely discussed so candidly; post-natal depression.

“He was never going to make it through because he was too big, so I had to go in and have an emergency caesarean,” she recalled of her delivery on the ABC program.

"They pulled Ernie out, he was a big baby, he was over 10 pounds and he was purple. I thought he was stillborn. He traced for a blood infection and went straight into the ICU for five days."

When she and her musician husband Keir Nuttall took a healthy Ernie home, the realities of motherhood began to sink in, and Kate was terrified.

"I did find myself struggling with just, you know, the basics of how to feed him, how to change him," the 37-year-old said.

"Why wasn't he sleeping? Why won't he stop crying? I guess I started to become neurotic in a way, for the first time in my life. Compulsively Googling symptoms, constantly thinking that we needed the emergency doctor to come out."

The feeling she was doing something wrong, or had missed the memo on how to be a mother, was something she found difficult to shake.

"There was a small voice inside of me saying that, you know, 'Ernie might be better off with a mother who does instinctively know what he needs'," she admitted.

"Keir was an incredible father right from the start. He ended up co-sleeping with Ernie for months while I was in another room because I just couldn't deal with it. So I suppose I felt a bit like a... a bit of a failure."

"Usually unflappable Kate was in a state that was often inconsolable, it seemed like," Keir said of his wife.

Her struggle - one that so many mothers go through - became the inspiration behind 'Zero Gravity', the song she will be performing at Eurovision this week as Australia’s entrant to the 64th edition of the eclectic song contest.

A refreshingly bold choice of topic to tackle while representing our country on a world stage.

Here's her performance in the first ever Australia Decides live TV competition held to choose our national representative. Post continues after video.

But for a long time after the birth of her son, the opera-trained Kate worried she may never even be able to sing again.

"Another thing that compounded my anxiety in those early months is that physically I was too tired to sing. All these muscles were weak and somehow broken. I guess I started to worry that it was never going to come back," she explained.

"Singing has always been like a pressure-release valve and then to not have that just, uh, made things a lot worse."

She said two things pulled her our of her depression - seeking professional help, and writing the lyrics of 'Zero Gravity'.

Her husband says the song is about "the feeling that you get when you shake off depression. When you finally wake up one morning and when you realise that it's not there today."

Kate added: "Having been through a period of feeling very low after the birth of Ernie, the song was part of the healing, in a way."

Kate Miller-Heidke will perform Zero Gravity in Eurovision's Tel Aviv semi final early Wednesday morning, with the grand final scheduled for Sunday morning. The contest will be aired on SBS.