Her EDS developed into severe gastroparesis, where food passes through the stomach more slowly than it should and became an eating disorder.
"It basically means there is a missing genome in my DNA, so my body isn't built fully as a normal person's body would be," Harley said.
"In my case, it's then developed into lots of other conditions.
"The longer I've gone untreated, the worse it has become because I've then developed lots of other conditions. It's just made life harder and harder."
Her condition would not have progressed as far had she received "proper treatment" or been diagnosed sooner, she believed.
The Department of Health was approached for a response.
Harley was diagnosed with EDS after her family paid for private healthcare, having explored what she described as every option available through the NHS.
"So it's there, the treatment is there, the medication is there, it's all there - you just can't access it on the NHS," Harley claimed.
Going without a diagnosis for a decade had a profound impact on her childhood, Harley said.
"It was 10 years without a diagnosis. It ruined all my youth, all the fun things you get to do as a kid - you go to school, you have friends, go on a date for the first time, have a job," she said.
"All that was just not possible.
"But as I've got healthier and I've been able to connect with other people from the same situation, it's really shocking how many other young people are just like me, having their whole youth stolen from them, because they can't get diagnosed."

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