The life-shattering moment I discovered my grandfather was my dad - after he raped my mother at gunpoint

A woman who was conceived after her mother was raped by her own father at gunpoint has bravely spoken out about the trauma of discovering her horrific family secret that led to her battle with anorexia.

Jodi Cahill, from Melbourne, received a letter from her estranged mother four years ago informing her of a secret she had kept for three decades - they shared the same father.

The 38-year-old told Daily Mail Australia in letters to come her mother detailed the years of abuse she had suffered at the hands of her father, Raymond.

I got the [first] letter in the mail without warning whatsoever. I was scared to go to my mailbox a few weeks after that. She [my mother] kept writing and writing and writing,' Ms Cahill, who was raised by her divorced grandmother - Juanita - after her mother developed psychosis, said.

'She virtually said "it’s about time I told you the truth of who your father was... you and I share the same father", and I was like "what?"

I was so in shock and disgusted. That night I tried to jump off a bridge. I didn't know what to do with it [the news].'

But with the terrible truth came a moment of clarity for Ms Cahill who now understood why her mother had 'hated' her so much.

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Her mother sent her this two-page letter and told her who her real father was. It was revealed Ms Cahill's mother was raped by her own father

This is the second page of the letter Ms Cahill was sent. She said she was scared to open her mailbox for weeks after the first letter

'Everything that happened when I was little really made sense to me. She was always in and out of hospital. She only told someone about it about 10 years ago,' the public relations executive said.

'I just thought she was always mental and the way she treated me, I just couldn't just understand any of it.

'She threatened to kill me with a gun once. She told the police she had a gun and she was coming for me.

'It must have been horrific for her every day to look at me as a reminder. Everything makes sense now.

'She told me: "Every time I look at you it's a reminder of what happened, it reminds me of him".' 

The 38-year-old now living five months without having the urge to go back to her old habits

A young Jodi with her father and her grandfather who sexually abused her mother from a young age

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Ms Cahill said her mother could not even look at her without thinking about her own father and what he had done

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She was raised by her grandmother when her mother developed mental health issues as a result of her abuse

Following her mother's confession, Ms Cahill's life started to unravel and she threw herself into her work running her charity organisation instead of dealing with her issues.

But soon she stopped eating and started to lose weight, and eventually she was diagnosed with anorexia.

'I slowly cut down on foods. My friends saw I was getting smaller and smaller... they saw me get to 46 kilos,' Ms Cahill said.

'I made sure I flushed food out of my system with laxatives.

'When I felt empty I felt okay. I could on concentrate on how empty my stomach felt, which is kind of ironic.

'At the worst point, I was about 34 kilos.'

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Ms Cahill went to live with her grandmother after she and her grandfather divorced. She said he had raped her mother at gunpoint

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The Melbourne public relations executive as a child (centre) with her mother on Santa Claus' lap

Ms Cahill's anorexia got so bad that she ended up in The Royal Melbourne Hospital.

'I was fed from a tube for about four months,' she told Daily Mail Australia.

After years of battling the condition, Ms Cahill said she never wants to go back to who she was before, even though she still has a long way to go.

Recently, she did a stint at the Northside Clinic in Greenwich, on Sydney's North Shore, where doctors helped her onto her road to recovery.

Her previous time there had been unsuccessful after she left the facility for six weeks to visit friends in Melbourne, and fell back into her old habits and lost 13kg.

But this time Ms Cahill is confident she can beat her anorexia.

'Every day is hard. This is first time in five months I haven’t touched anything related to eating disorders. I just want to focus on how I can help. I'm as healed as I can be,' she said.

'It's all about your mindset. You can have the best doctors and the best friends, but if you don't hate the anorexia as much as you hate yourself, you won't beat it.'

Ms Cahill hopes that in sharing her story she can help other beat the condition.

She said she wanted to help as many people as should could. 

Daily Mail.