I'm a former breast surgeon who's had breast cancer twice. I had to retire early because of how much pain I was in.

• Liz O'Riordan is a former breast surgeon based in the UK.
• In 2015, at the age of 40 she was diagnosed with cancer for the first time.

This as-told-to essay is based on a conversation with Liz O'Riordan, who was diagnosed with cancer twice at the age of 40. It has been edited for length and clarity.

As a consultant breast surgeon in the UK, I thought I knew everything there was to know about breast cancer. Then, in July 2015 at the age of 40, I was diagnosed with stage 3 breast cancer myself.

As soon as the radiographer put the probe on my breast, I looked at the screen and saw a cancer. I didn't need to wait for the biopsy or the results or to find out — I knew what it was, and I knew it was big. Because I was young, I knew I would need chemo, possibly a mastectomy. I even had a good idea of my chances of being alive in 10 years.

I started treatment right away

In that moment, it was like something switched off inside me. Because I've looked after men and women who've died of breast cancer, it was too much to cope with. It felt like it was happening to someone else. Two weeks later, I started chemo. I quickly realized that despite having prescribed chemo for so many patients, I knew nothing about how it actually felt. I had no idea how ill it could make you or how to cope with the brain fog, the instant menopause, the severe constipation, and losing my sense of taste.

After five months of chemotherapy, my cancer seemed to have completely melted away, according to my scans. I went to get the results of that surgery on December 23rd. In the waiting room, I was surrounded by couples who were probably about to find out that one of them had breast cancer just days before Christmas. I was so relieved not to be in that position, I really thought it was all over. However, it turned out that there were still over 5 inches of cancer left in my breast and lymph nodes. It hadn't shrunk.

I knew what that meant. My chances of survival had suddenly dropped, it meant more surgery and more radiotherapy. I couldn't process it. But of course, I had to do it. So, I had more treatment, and it was really, really hard, particularly experiencing the menopause at 40.

Going back to work with cancer patients was hard

It was also really hard going back to work, having had cancer myself. I didn't want to perform surgeries because I was experiencing chronic pain and knew how much pain I might give my patients. I also found it difficult because when I told someone they had cancer, I wanted to say, "yes, it's shit! I know it's shit, I get it!" But as a surgeon, I couldn't really do that because we're supposed to be factual and, if anything, positive.

Two and a half years after my first operation, in 2018, I found a nodule of scar tissue under my arm. An ultrasound showed a less than an inch recurrence of cancer on my chest wall. I had to have a mastectomy, and I was confronted with new fears: how am I going to cope with being flat chested? I know it's vain, but you don't consider what your breasts mean to you until you lose them. Then I had to deal with another problem: the pain I was experiencing in that area meant I lost mobility in my left arm, and as a result I couldn't operate anymore. I was forced to retire, and I wasn't sure what to do next, but I came to realize that people diagnosed with breast cancer were turning to the internet for answers to the questions their doctors didn't have time to give them.

The problem is that anybody can put whatever they want online with no need to evidence their opinions. That's why I started blogging and putting my own videos out there — as a surgeon, I hope to be a voice of reason and try to help people as someone who's been on both sides of the operating table. I used to stick to just talking and posting about breast cancer, but I felt that as a doctor I wanted to help a wider audience. I was getting lots of posts sent to me that made my blood boil, mainly around what I call "nutribollocks," influencers with millions of followers who say that mushrooms or kiwis cure cancer. It's rubbish, but because they call themselves nutritionists or experts, people believe them.

As an actual expert, it makes sense for me to try and dispel these myths and share actually helpful information.

Before I got cancer, I was a very boring 40-year-old because all I did was eat, sleep and work. Getting cancer was a wake-up call that life is not about work. Now, I volunteer at a hedgehog shelter, I walk the dogs, I do gardening. It's a shame that it took cancer to make me a more well-rounded person, but I hope to continue helping people through speaking about my experience and sharing my knowledge for years to come.

Liz's new book is available for pre-order here. Series Two of her podcast "Don't Ignore The Elephant" is out in March.