Doctors 'laughed' at her concerns, but this mum knew instinctively something was wrong.

At 35 years old, mum-of-two Deborah James was fit and healthy. She had been a vegetarian for 25 years.

But when she was diagnosed with stage three bowel cancer just before Christmas last year, she realised that you are “never too young” to be affected by the disease.

A secondary school teacher in Surrey, Deborah told The Sun that if it wasn’t for her persistence, she would never have been diagnosed when she was.

She first noticed changes to her bowel habits "a couple of years ago", but doctors told her she was suffering from irritable bowel syndrome (IBS).

Six months before her diagnosis, she noticed her symptoms were getting worse.

"I started going to the loo lots," she told The Sun.

"Then I started passing blood. That’s the point I thought, 'Something is wrong'."

Despite going to the doctors for three sets of tests on her blood and stool samples, all of her results "came back normal".

"I kept going back to the doctors. I had tests and they came back normal. But I kept thinking, 'It's not normal to s*** blood...it's not IBS'. I knew there was something wrong."

On the blog she started to document her cancer journey and to help spread awareness about the disease, Deborah admits she was "laughed at" by health professionals.

"If only for once someone believed me earlier that I wasn't 'crying wolf'...when in my normal nervous GP 'question time' I tell the doctor I think I have bowel cancer...not once but 3 times over the course of 6 months!" she wrote on her Bowel Babe blog.

"I was still losing weight, passing blood, going what felt like 100 times per day and feeling shattered. I knew there was something wrong with me, a sixth sense if you will, because for the first time I was afraid – very afraid about taking this further."

LISTEN: Tina Harris on surviving breast cancer on I Don't Know How She Does It.

Deborah took matters into her own hands, making a private appointment to have a colonoscopy, where she finally saw her tumour for the first time.

"You feel numb, shocked, like you're in a dream that's happening to someone else," she said of discovering she had cancer.

"Then we had to face telling the kids, your first instinct as a parent is to protect them. But actually the best thing was to just be open with them," she said.

"You don’t say 'Mummy is going to die'. We told them I was going to have an operation, and chemotherapy to make her better. It was very emotional telling them."

Since her diagnosis in September, Deborah has had surgery to remove a third of her bowel and has just started six months of chemotherapy, which will be administered once every two weeks.

Now, she's encouraging others to put their squeamish selves aside and start talking about their bodily functions - something that could have caught her bowel cancer much earlier.

"The only times we talk about poo is when we have kids, or we're in hospital," she said.

"When you have kids you're always talking about their pooing habits and when you're in hospital medics are only interested in asking about what your bowels are doing and if they’re working or not. Nobody else talks about it.

"If you’re experiencing problems don't be scared to take pictures to show your doctor."