The former nurse, now 37, who lives in the Hawke's Bay, said after four years of being together they decided to start a family.
However, Amber said a doctor advised them there was only a two per cent chance of being able to conceive naturally, so in December 2015 they signed a contract for IVF treatment.
After one cycle, she said they were extremely fortunate to have seven embryos.
"I was so happy, it was like winning the Lotto," she said.
Then John changed his tune, she said.
Amber says John threatened to only sign the consent form for her to use a embryo if she paid him $3000 and left him off the birth certificate, so he wasn't liable for child support, she said.
"At that age, I was starting to feel like my eggs were drying up and this could be my only chance of having a baby," she said.
Amber agreed and her daughter, now aged 6, was born.
The couple separated but two years later, Amber desperately wanted another baby and asked John for permission to use another embryo.
Under New Zealand law, both parties must consent to every stage of the IVF process, including using frozen embryos, which is the genetic material of both parties.
"He said to me 'if I consent to it, you have to do something for me'. So [my second child] was actually conceived naturally because I was forced into having sex with him," Amber said.
"It was almost like, if there's a God, he was going 'now I'm really going to mess with you' because the chances of us conceiving naturally were less than two per cent."
Just weeks before New Zealand went into its first Covid-19 lockdown, another embryo was implanted into Amber's body which resulted in the birth of her third child in December 2020.
Now, Amber wants another child but she says John is refusing to sign the consent form to use any of the remaining embryos.
Police confirmed to the Herald on Sunday they were investigating a man who had allegedly been using frozen embryos to blackmail his ex-partner into giving him sex and money.
"It would be inappropriate for police to comment further at this time," the police spokeswoman said.
The Herald on Sunday made several attempts to contact John for comment but did not get a response.
Amber said it took her a long time to realise John's behaviour was sexual and emotional abuse.
"Even as a health professional I wasn't able to recognise what was going on, which sounds stupid."
She said paying John money was much easier than giving him sex.
"Every time we were intimate, I had to go have a shower after... it was just this horrible thing, I knew I had to just suck it up and give him what he wanted."
Amber said everyone has a different opinion about what embryos mean but to her they were potential babies.
"I know not all of them will be viable but when I look at my 22-month-old, I think 'he sat in the freezer for three years', and look at him.
"Those embryos mean so much to me, I have kids to them."
The single mum of three said she was frustrated because the horrible situation could have been avoided if the IVF screening process had been more thorough.
"There's counselling provided with fertility treatment and for whatever reason our value system wasn't really discussed, like what happens to the embryos if we separated?," she said.
In the IVF contract - seen by the Herald on Sunday - John and Amber agreed that if either of them died, the embryos would be disposed of.
However, there is no provision in the contract for what happens if the couple separates.
"I've effectively been put in a vulnerable, exploited position because what I regard as important is different to what [John] regards as important," Amber said.
Fertility Associates chief executive Alex Price wouldn't comment specifically on the couple's case but said; "If people do choose to have counselling as part of their IVF treatment, then the counsellors look to cover the implications of treatment such as what to do with embryos".
Price said they couldn't cover off every possible event, and people may change their mind, even after they have signed the consent form, as they are able to do.
"So even if a patient says, 'if we split up, I consent to the embryos being used', in the event of separation they may change their mind.
"Effectively a consent at this point is not binding. We expect couples to work through their disagreements - as they would have to work through... other life situations; child custody, pets, houses etc."
University of Canterbury associate law professor Dr Debra Wilson described the situation as "horrible", as legally Amber could not use the embryos without John's consent even if they had reached some sort of agreement before starting IVF.
"Even if the issue of what happens to the embryos in a divorce had been discussed and written into the contract, this would not necessarily be sufficient to override the man's wishes in this situation."
Wilson said the status of embryos was a matter of international debate - are they "property" which could be the subject of a contract or a will?
Or are they "life forms", as some people believe that life begins at conception?
"(The) current thought is that embryos are probably somewhere in the middle, so deserving of respect as future life. This leaves the legal position uncertain," Wilson said.
