"Looking at them was triggering for me for a long time. I don't have many photos from that period, I deleted most of them because they were painful to look at," she wrote in her post.
Olivia was 19 years old when the images were taken and despite her health battles, she said modelling agencies would reassure her she "was doing really well and should be so proud of myself'.
"This was the beginning of a six-year battle with an eating disorder, body image issues and a terrible relationship with food and exercise," Olivia said.
"I still experience a lot of emotions when I look at these photos. I feel deeply sad remembering my mindset at that time, and seeing how young and vulnerable I was."
Olivia, who took home the prestigious Miss Universe Australia beauty pageant title in 2017, said she now feels an "overwhelming sense of relief, pride and gratitude" after acknowledge just how far she has come over the years.
"The primary feelings I have now are positive," she said.
The model turned speech pathologist went on to encourage her 160,000 followers battling with mental health issues, to speak up.
"World Mental health awareness day is this Saturday 10th October. I know it can be really confronting and scary to talk about personal experiences with mental health, but maybe this weekend you could try to open up to someone that you haven't before," Olivia wrote.
"I personally find it really freeing, the more I share my experience the easier it becomes. I encourage you to do the same — speak up and shake off the stigma."
Many of her fans went on to thank her for her "vulnerability" and giving raising awareness about eating disorders.
"Thank you for your vulnerability and giving us a much-needed insight into what it means to experience an eating disorder. I'm so glad you're well and happy," one fan wrote.
"It is such an awful illness to go through — that look of emptiness and sadness is so terrifyingly scary. It's amazing that when you're in it you can't see it but when you're "out" of it, it's the thing that speaks volumes," another fan wrote, adding, "I'm so glad you were able to find your way to recovery. I have too and am so grateful!"
Earlier this year, the model called out a follower for making an "absolutely disgusting and disgraceful" remark on one of her bikini photo's.
"You're too fat to be on Instagram. You should take this down it's embarrassing," it read.
Just hours after posting it, Olivia took to her Instagram Stories to share the response with her fans.
"People who comment things like that are a big part of the reason young girls develop issues with their weight and bodies," she said about the remark.
"They are a big part of the reason I had an eating disorder for 6+ years.
"I am a size 8 which usually is irrelevant to the conversation, but if I am being called fat as a size 8, imagine your size 10, 12, 14, 16, 18 woman and the comments they receive."
Olivia has always been vocal about wanting to be a health and happiness role model for other women. She celebrated winning her Miss Universe Australia crown with a glass of champagne and a Big Mac.
During her time on stage she also opened up about her "disordered eating", revealing her weight once dropped below 49kg, and she knew she was "in trouble".
"For my height (173cm) that's just not OK and it was all to look good in a photo and for what … I wasn't happy," she said.
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• The Word
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
