The Department of Social Services tried to prevent a woman who lives in pain “pretty much 24/7” from accessing the disability support pension, arguing she was fit for work because she volunteered at a children’s hospital.

But in a rare win for an applicant living with chronic pain, Natasha Thomson was granted access to the $450 a week payment after a two-year battle that ended up at the top level of the administrative appeal tribunal.

The 26-year-old Melbourne woman had lived on the $277-a-week Newstart payment in the meantime, racking up a $5,000 credit card debt as she struggled to pay bills and cover her medical costs.

The case got to the general division of the tribunal only because the department appealed after a lower level tribunal sided with Thomson.

“It’s hell,” said Thomson, who represented herself at the tribunal. “It shouldn’t be this hard to get the help that we need.”

To access the disability support pension, people must prove their condition is “fully diagnosed, treated and stabilised” and that they are unable to work at least 15 hours a week.

The department argued Thomson’s charity work shifts were often longer than three hours and that, with her work as a nanny, this proved she could “sustain work activity or other tasks for periods of three or more hours per day”.

But the tribunal said her volunteering and nannying took place with a “benign employer”. At hospital, she would watch movies with sick children and comfort infants and other children who could not take part in physical activities.

Thomson told Guardian Australia the department’s arguments were hard to take because the hospital was “a positive place” for her.

She described her pain as like having “a white hot poker sticking through my abdomen”.

“My chronic pain is pretty much 24/7,” the former early childhood and primary education student said. “So for me to go into the hospital, I’m going in there in the headspace where I just push the pain down basically.

“I love volunteering because it’s a way to give back; it’s about helping these other people in a way that I’m good at.

“And because it’s volunteering, I can say, ‘I’m not up to it this week,’ and they’re OK with that. I’m not going to get fired.”

Until the tribunal verdict, Thomson was among the record-high 200,000 people who are now on Newstart while sick or with a disability.

Joel Townsend of Victoria Legal Aid, which provided some advice to Thomson, said the organisation was taking on more disability support pension cases.

“That is, we think, partly to do with the fact that there have been quite significant hurdles put in the way of people who are seeking to obtain [the disability support pension],” he said.

The rate of successful claims has fallen to 30% after the criteria were tightened by successive governments. Most people do not appeal to the tribunal, and the changes have made it particularly difficult for applicants like Thomson who suffer chronic pain.

“For many people, they’re not taken seriously,” Carol Bennett, the chief executive officer of Pain Australia, said.

Bennett said the definitions used to assess people for the disability pension did not include “chronic pain conditions that are non-specific”.

“These conditions are not easy to diagnose or treat,” she said. “These are very debilitating conditions. When you can’t work, it creates a real poverty trap.”

Doctors had suggested Thomson had endometriosis, but in her application she relied on a chronic pain diagnosis.

Darren O’Donovan, an administrative law expert at La Trobe University, said he hoped the case meant others would not have to “engage in a unrealistic hunt for diagnosis and treatment before they can get basic support”.

“The fact that a person with disability tries to help out charities in their community needs to be kept distinct from their ability to sustain work in a commercial environment,” he said.

A doctor contracted by the department to assess Thomson’s medical records also argued her claim should be denied because she had undertaken multiple overseas trips.

“She would appear to only be impaired in Australia,” the doctor wrote in a report cited by the department.

Thomson said it “really sucked that those little things were being used against me”.

The same doctor noted she had not tried a treatment that Thomson said “would have involved putting me into medical menopause”.

“I was 25,” she said. “I would still like to have my own children. So that hit me hard emotionally.”

The tribunal found that Thomson’s chronic pain condition was “permanent … fully treated, fully stabilised and more likely than not, in the light of available evidence, to persist for more than two years.”

Giving evidence, she said her “lower back and hips were aching so much that I could barely stand to be sitting in a chair”.

She had a panic attack before the hearing and “a really big spike in my pain level” when she got home. “[That] was not entirely unexpected because stress is one of my big triggers for pain,” she said.

“So I didn’t sleep very well that night. I cried a lot when I got home.”

Last month Thomson learned the government would not appeal again.

A spokeswoman for the department said: “The department cannot comment on individual cases.”