It was in that moment the 34-year-old, who weighed more than 90kg at her heaviest, decided to change her lifestyle. And she did just that, transforming from a size 20 down to a happy 8-10 in just six months.
"It was super-confronting and tough. I just didn't want to be that woman anymore," Gallagher told news.com.au.
"I had ups and downs with my weight, but I was never that heavy. With my first child [now 7 years old] I got close to 80kg, but this time, with my second child [10 months], I really blew out and let myself go."
Gallagher suffered from postnatal depression (PND) with her youngest child and was also recovering from a broken arm after falling down a flight of stairs, which she said contributed to her weight gain.
"I didn't have PND with my son, it was a whole new feeling with my little girl. I put so much pressure on myself. I thought, 'I should know what I'm doing', having had one before.
"My brain was really playing tricks on me and I couldn't understand, being a devoted mother, why I felt this way."
Knowing she had to take control of her life again, Ms Gallagher joined a local gym last November. Once she started clean eating and training her journey to happiness and contentment began.
She signed up to a six-week challenge and won. She also came first in a national competition through the gym and went on to win AU$5000 — she was judged on her weight loss, before-and-after images and overall lifestyle changes.
"I never want to be that overweight, depressed woman again. She's just somebody I used to know," Gallagher said.
She had never been a "gym person" and signing up was daunting.
She started with three sessions a week.
"It broke me. I had no form and also suffered from ab separation after giving birth. I was in agony and I wasn't lifting correctly — I wasn't shown how to do things correctly."
One of the mothers from her son's school introduced her to another gym where she took part in group workouts.
"Since then I haven't looked back," she said.
Gallagher now goes to the gym six days a week, mainly before school drop-off at about 4am.
She started seeing results after two weeks — a body scan showed her visceral fat (the fat around the organs) had also dropped.
"It added years onto my life. Then I started to notice I was dropping numbers on the scale and also my measurements, and I wanted more."
Her workouts consist of weights, endurance, strength and conditioning and high intensity classes.
"I feel like a whole different person. I've totally transformed and changed my life. I just never want to go back to that person. I feel like I am a better wife and mum with more energy for my family."
Her words of advice for anyone looking to improve their lifestyle is not to listen to that "inner b**ch telling you, you can't do it".
"If I can do it, you can do it … the world is yours."
DAY ON A PLATE
Breakfast: Half a banana and coffee before training, followed by a protein shake, coconut YoPRO with raw almonds, berries and shredded coconut, and a gluten-free muesli bar.
Snack: Protein ball, rest of the banana.
Lunch: Homemade tandoori chicken pizza.
Snack: Two boiled eggs with cottage cheese and curry powder.
Dinner: Homemade chicken schnitzel with vegetables and sweet potato chips.
Dessert: Protein pancakes with sugar-free maple syrup, mixed berries, cottage cheese.
Drinks: Include up to to three litres of water a day.
