The 29-year-old actor and musician was diagnosed with brain cancer back in August, after discovering he had a seven-centimetre tumour that had grown over his right frontal lobe in his brain.
On Wednesday, the Home and Away star sat down with Carrie Bickmore to share his story with The Project, admitting it was down to luck that he was with us today.
"The surgeon said if I hadn't gone to the hospital that night I would have died in my sleep that night. It is just sheer luck that I went in when I did and everything happened the way it did otherwise I wouldn't be here," he admitted.
The Perth native, who became a household name following his time on X-Factor, experienced headaches regularly - which he believed to be a side effect to his lifestyle.
"Anything that may have been a symptom, I just put down to normal life. Headaches - I played sports and copped a million and one knocks in the head," he said,
"You never thought - it may have attributed to it or not. You wake up with a bit of a hangover and you think, 'it is a headache from having a drink,' but this particular time I hadn't gone out at all and I just had a really bad headache. It grew from that.
Recounting that fateful Sunday, August 6th evening, Johnny shared, "My sentences were not making any sense. My words were jumbled up. It became alarming to [my girlfriend]. She said maybe we should go to the emergency department."
"I went in on Sunday night. The surgery was Monday. They started at 2pm and I got out at about 10:00pm."
"It took about eight hours to remove the tumour. It was seven centimetres so it was really quite large in my right frontal lobe. You can see the scar."
"They knew it was a tumour. They could only remove 95 percent of it due to where it was positioned, close to the nerve endings, I believe. So the remaining 5 percent they decided radio therapy and chemo therapy was the best option for it."
Johnny's candid chat saw the star admit he'd originally thought his symptoms could have also been sign of depression.
"Initially I thought I was just depressed. Id even gone to the doctor, and the doctor said 'You know, all the symptoms seems like depression'."
But after discovering what was really happening inside the 29-year-old's brain, it was clear it was something else.
"After having found the tumour, the neurosurgeon said it was not depression at all, it was because there was so much pressure being put on your brain it was causing all these different symptoms."
While there's no way to tell how long Johnny has had the tumour, doctors have said "it could have been potentially growing from two years to 10 years."
Johnny, not only brave, but ready for what will be a big battle.
For the next six months he will undergo radiotherapy and chemotherapy in a bid to get rid of the remaining 5% of the tumour.
Despite the whirlwind of everything, Johnny has used this experience to not only better his life, but to help others.
The 29-year-old has been named the national ambassador for the Walk For Brain Cancer.
"Looking back I wasted a lot of time just doing things that at the time was great, I had a lot of fun and what not, but now I feel like I really want to focus on my work and career and things that make me happy," he said.
"Whether it is music or acting and just entertaining. You have an epiphany about life almost. You appreciate it a bit more."
"It could have quite easily been over for me that night. It is almost like having a second chance and you appreciate things a lot more and you don't take things for granted as much."
If you'd like to help out head to walk4braincancer.com.au.
For Johnny's remarkable full interview on The Project, check it out below!