Ollie was on a camping trip when his mum noticed something wasn't right.

Every parent knows that gut feeling when something's not quite right with their child.

For Anna, that moment came during what should have been a joyful family camping trip, when her usually vibrant, funny little boy Ollie just wasn't himself.

The family was off the grid at Upper Allyn in NSW, celebrating what should have been a magical milestone — Ollie's fifth birthday. His only wish? To finish their adventure with some beach camping.

But as Anna watched Ollie sitting by the campfire, her heart sank.

Watch: A day in the life of a cancer researcher. Post continues below.

"He was really weak. His lips were the same colour as the rest of his skin," she told Mamamia. "When I was changing him that night, I noticed a rash on his body."

Her husband Andrew tried to reassure her, suggesting it might just be an insect bite — they were out in the bush, after all. But she couldn't shake the feeling something wasn't right. Erring on the side of caution, they decided to pack up early.

"We broke the news to Ollie saying, 'Buddy, we've got to go home and go to the doctor. Once we get the all clear, we'll come back to the beach.'"

Ollie before his diagnosis. Image: Supplied.

At the doctor's office, "it all kicked off". Before they knew it, they were on their way to the hospital, where Ollie underwent test after test — and the nervous wait for answers began.

"We started to see the rash had started spreading… I saw the spots coming up on his eyelids in real time," Anna says.

When Andrew arrived at the hospital, they quickly learnt that Anna's maternal instinct was right: it was serious.

"The doctors walked in and I saw a person with a badge, and it was an oncologist. The first question was, 'Do you know much about leukaemia?'"

With that one sentence, Anna's world crumbled. The next few minutes passed in a blur as her head spun with questions.

"It was like I was looking at the doctors talking, and their mouths were moving but I was in this whirlwind. I was looking at Ollie and he was looking at me, and looking at my husband. He was trying to be reassuring, but I could see the fear in his eyes," she said.

"Everything we had planned up until this point was going to dramatically change."

Ollie in hospital. Image: Supplied

A devastating diagnosis.

There was no time to wait. Ollie needed an immediate red blood cell transfusion. But after a traumatic experience with a cannula hours before, their usually brave boy was terrified.

"I remember him screaming, losing all control of everything… 'Please stop! I'm not ready. Give me one more minute,'" Anna says.

Then came the four words that would haunt any mother: "Mummy, make them stop."

"When you're a parent, and you birth your children, you think you're going to do everything you can to protect them and ensure their safety. Knowing strangers had to hold them down and you just have to trust the process," Anna said.

"He didn't understand it was to save his life. I just broke down. I can't protect him, but by giving him the blood, we were protecting him."

Ollie, centre, with his family. Image: Supplied.

Instead of joining his friends for his first day of kindergarten, Ollie faced a different kind of beginning. Separated from his three older siblings, his world of playground adventures and finger painting was replaced with chemotherapy and endless tests.

"We were trying to navigate what's going to happen with the kids, school starting, and a diagnosis we knew nothing about. We were really in limbo," Anna said — an experience she wouldn't wish upon anyone.

During their darkest days in hospital, the family discovered 'Captain Starlight' — the Starlight Children's Foundation's superhero mascot, who visits sick kids in hospital to help them cope with hospital and treatment.

On those seemingly endless days, when Ollie could barely leave the ward, these moments of pure joy became their lifeline.

One day in particular stands out for Anna: when Ollie received his Starlight wish — his very own go-kart.

"It was so far out of reach because of everything we'd gone through with his diagnosis. We didn't think he'd be able to do it," Anna says.

"It was probably one of the happiest days of his life and meant everything to us as a family."

Ollie after treatment. Image: Supplied.

Taking it day by day.

This month marks three years since Ollie's diagnosis. And while he's doing well, the family still deals with the lasting trauma of cancer.

"It's not the way kids should grow up. It's not something anyone should ever go through, especially kids. They shouldn't have to experience stress until later in life," Anna says.

Today, Ollie looks like any other energetic eight-year-old. He just celebrated his birthday with that same camping trip that changed their lives three years ago. He's back at school, surrounded by friends, and he loves life. But beneath the surface, the scars remain.

"He remembers the scary moments… he's still fatigued even though he wants to give it his all. I still see those effects. I know there will be things that happen in the years to come, but we're trying to take it day by day," Anna told Mamamia.

Ollie with his go-kart from his Starlight Wish. Image: Supplied.

Anna's message to other parents is blunt but simple: cancer doesn't discriminate.

"You hear of it in the news and community, but it never once crosses your mind it could be your child that could be diagnosed," she said.

"When it happens and you're amongst these other families, you realise it's extremely rare, but it's happening every single day."

Ollie's family are sharing their story in support of the Starlight Foundation's Super Swim Challenge. Super Swim encourages Aussies to swim during the month of February and raise $5 million to bring joy to sick kids in hospital. You can register to take part in the challenge here.

Feature image: Supplied.