Pregnant mother Nivek Johnson was weeks away from giving birth when doctors delivered heartbreaking news no-one ever wants to hear

A young mother-of-three was dealt a devastating blow after she was diagnosed with a life-threatening cancer when she was weeks away from giving birth.

Canberra woman Nivek Johnson, affectionately known as Niv, was 34-weeks pregnant when she was diagnosed with triple-negative breast cancer. 

The 37-year-old nurse had felt a firm lump in one of her breasts and initially thought it was mastitis - a painful infection of the breast tissue.

'For a week or two I just did some home remedies to try and clear what I thought was a blocked duct,' she told Daily Mail Australia.

'It never ended up clearing so I went and saw my GP and I was put on some antibiotics, but those weren't effective.'

An ultrasound, a mammogram and a biopsy the following week revealed  the lump was something much more ominous.

Ms Johnson was in disbelief after the doctor told her she had a fast-growing and aggressive tumour.

'It was definitely a rollercoaster coaster of emotions,' she said.

'It was shocking and I'm still trying to wrap my head around it really.'

A week later she met with a team of oncologists who devised a treatment plan for her.

'They decided it was best to start the treatment while my bub was still in utero,' Ms Johnson said.

'I had three chemotherapy infusions while my little baby was still in my belly and then I had a small break in order to deliver him via C-section.'

Ms Johnson's closest friends set up a GoFundMe to help ease the financial burden and take care of her family while she is fighting cancer.

'She is as tough and stoic as they come,' they wrote.

'Less than 10 days after baby Felix arrived safely into the world, Niv resumed her fourth round of chemo, which will be followed by a grueling regime of surgery and radiation.

'It's no secret that adding a newborn into the family dynamics is no easy feat, but having the birth of your child overshadowed by cancer is something nightmares are made of.'

Generous Aussies have already donated more than $25,000, which will go towards a meal delivery service, hiring a nanny for the kids and covering any treatment costs.

Ms Johnson expressed her family's profound gratitude for the support they have received during this difficult period.

'We are so appreciative,' she said.

'It's a really odd thing to ask for help, so setting up this GoFundMe is probably not something I would have ever done for myself.

'We're just so blessed and fortunate to have such an amazing support network around us.'

Ms Johnson said juggling the newborn period, sleepless nights and getting used to more intensive chemotherapy has been a challenge. 

She said it has been difficult because she isn't able to be as active around the house.

'I was the primary care giver but now sometimes I need to rest or I'm not able to take kids to school,' Ms Johnson said. 

'I can't keep the houses clean as I usually do, I can't cook as much as I used to and just all those sorts of things.' 

She explained her husband has been a huge help and an amazing carer, but he will have to return to work at the end of August. 

'At the moment it's just one day at a time, I haven't really looked too far into the future yet,' she said.

'Returning to work after maternity leave was one of my goals and that's sort of been put on the backburner now.'