Prior to being diagnosed with endometriosis, Sinead was told she had Pelvic Inflammatory Disease, The Mirror reports.
"At first I was diagnosed with Pelvic Inflammation Disease and despite being on antibiotics, nothing helped," she recounted.
"It wasn't until January 2016 that I was diagnosed with endometriosis and I was finally taken seriously.
"I underwent a surgery called laparoscopy so doctors could see what was going on inside my stomach.
"It was then that they realised I had the condition and they removed as much of the endometriosis as possible.
"However I had no idea it was a reoccurring illness and the pain was back just three months later."
Sinead explained that in addition to battling pain, anxiety and stress, endometriosis's potential impact on her fertility has also been difficult to come to terms with.
"My condition can cause infertility, which causes me huge amounts of anxiety; its absolutely terrifying,” she said.
“I want to have a family one day so having a hysterectomy isn't an option for me right now and I don't think it ever will be.
“Another doctor told me to have a baby now if I want to ease my endometriosis; I was only 18 years old at the time.
"But I'm single and being told that as a teenager hit me like a rock as it showed there's little real hope for anyone diagnosed."
But Sinead has taken up the challenge of raising awareness about endometriosis and sharing her own experiences on her blog.
“If we all stand together against this awful condition then we will help others understand and hopefully no other women will feel alone in this fight," she said, the Mail reports.
"Living with a long-term invisible illness is hard but you cannot let endometriosis take over."
Her advice to other women battling endometriosis?
"You've got to find something in each day to reach, even if that's getting out of bed in the mornings when you're feeling drained and no emotion towards anything," she recommends.
"One small positive thought in the morning can honestly change your whole day! A negative mind will never give you a positive life."
One in ten women in Australia have endometriosis. You can find more information and support on the Endometriosis Australia website.