Lindy Waldron developed ovarian cancer which was wrongly diagnosed as irritable bowel syndrome (IBS).
The 59-year-old librarian, from East Sussex, said: "I began to experience right-sided abdominal pain, which became persistent and eventually kept me awake at night.
"Very worried and convinced I had bowel cancer, I visited my GP.
"She felt my abdomen and couldn't detect anything abnormal. Her diagnosis was IBS, but seeing the worried look on my face she agreed to refer me to a gastroenterologist.
"He also examined me abdominally and recorded 'no obvious mass'. Thankfully, with private health insurance, it was only a short wait for a colonoscopy to rule out colitis.
"The procedure was difficult and painful and although the results were normal, my ovary on the right side was seen to be protruding against the intestine.
"A week later I had a trans-vaginal ultrasound (TVU) and during the scan I realised something was very wrong.
"The sonographer ran to find the consultant with the results. I remember sitting alone in the car in a complete state of shock.
"The consultant rang me later with the bad news: I had a large irregular complex mass behind the uterus and extending to both sides of the pelvis.
"I was referred urgently to a gynaecologist. When I rang my GP to tell her I might have cancer, she was lost for words."
Mrs Waldron, who was 54 when she was diagnosed with ovarian cancer, is now in remission and has regular check-ups.
She previously worked as a community nurse and has adult children.