For years, Rebecca Birnie felt as though her life was unravelling due to a serious medical condition doctors failed to discover.

The 38-year-old mother from Moosonee, Ont. had lost her job, her home and custody for her twin boys due to near-constant headaches, slurred speech and seizures. She visited the hospital 23 times over the span of two years and was frequently brushed aside as doctors prescribed painkillers, which failed to provide long-term relief for her headaches.

"I didn't understand what was going on," Birnie told CTV News. "They were doctors. I figured they knew what they were talking about."

At work, colleagues thought she had developed a drug problem. Despite drug tests that came back negative, she eventually lost her job.

Birnie is emotional when she recalls that period in her life.

"I was sick and I felt no one was listening," she said. "I had nowhere to turn and I had lost all hope to that point. I didn't even want to be here anymore."

In July 2016, Birnie collapsed in her mother's home. She was transported to a clinic affiliated with Weeneebayko Area Health Authority, where she demanded a CT scan. She was sent to Timmins, Ont. where doctors found a massive six-centimetre tumour in her brain that they suspect had been growing for 10 years.

"I felt vindicated (because) there was a reason behind the way I was acting," she said.

Birnie is speaking out about her story after CTV News reported about medical errors in Canada and how patients face a difficult task in any litigation against their physicians. On July 14, CTV News put out a request to speak with any patients who believed they suffered from a medical error. Among the dozens of responses, Birnie's is the most shocking.

"I don't want this to happen to anyone else," she said. "It's been awful. It's been hell and I think people need to advocate for themselves and if they know something is wrong to pursue that and don't just let it go."

After doctors in Timmins discovered the tumour, Birnie was sent to Health Sciences North in Sudbury, where it was removed. Still, she is left with permanent damage to some brain tissue, lost part of her vision and needed to learn to walk again.

She is on powerful medication to control seizures, but is now back working and has custody of her boys once again.

But she still has questions.

"From someone who had never gone to the hospital very often before to all of a sudden  coming in weekly bi-weekly so many times  - why wasn't that investigated?" she said.

Dr. Ryan DeMarchi, a neurosurgeon at Health Sciences North, was the doctor who operated on Birnie three years ago and said her condition at the time was a "life threatening situation."

"There is no question that this is a very large brain tumour which required a challenging and very invasive brain operation to remove," he said. "This would be one of the largest tumours that I've operated on."

DeMarchi added there is about a 10 per cent chance Birnie's benign meningioma tumour returns, though doctors aren't entirely sure what caused it. He said anyone experiencing a prolonged headache-- particularly if they also suffer from nausea and vomiting-- should seek help from a medical professional.

DeMarchi  did not comment on what could've caused years of misdiagnoses, instead adding that catching a tumour "early on is very valuable, but that is not always the case."

Medical errors aren't entirely uncommon in Canada. In 2018, more than 900 medical lawsuits were filed. Researchers say about half of these cases are considered preventable.