So when I got a pain in my leg in August 2004, I assumed it was a pulled muscle, from all the running and karate I'd been doing.
I ignored it for two weeks, but eventually went to the doctor, who referred me to the local Vein and Thrombosis clinic as a precaution.
While I was there, a nurse heard my cough that I'd been suffering from for a while. I hadn't thought anything of it, but she suggested a chest X-ray.
The X-ray showed a shadow on my lung, but I still assumed it was a chest infection.
It wasn't until a week later that I saw my chest X-ray for the first time. It looked like I'd swallowed a golf ball. There was a big white blob on my right lung.
But it wasn't until I was told they had to take a biopsy that it all clicked. I had lung cancer.
It was the weirdest feeling. It felt like it wasn't happening to me. I started making jokes and just wanted to know what would happen next.
The tumour was classed as inoperable and was growing quickly, so I was offered chemotherapy and radiotherapy.
It really hit me hard. Within 24 hours of the first dose of chemo I was violently sick. After November's dose, the decision was made that my body wouldn't be able to cope with any more.
Fortunately, this was when we discovered that the tumour had actually shrunk - the chemo had worked. My consultant then contacted a specialist at Guy's Hospital in London, who was now willing to operate on the tumour.
In January 2005, it was cut out and by May 2005, I was given the all-clear.
I stayed positive almost all the way through and was lucky that my friends and family always treated me normally, even when I got down to 6 stone. They'd still come round and take the mickey out of me and we'd have a good laugh.
Obviously, there were times I wanted to give up. One day, I said I wanted to die. My friend just told me not to be so stupid and said she'd remind me what I'd said in a year, once I was cured. And she does exactly that.
Now I play golf three times a week and have a pretty normal life. I was lucky it all happened so quickly and I'm here to tell my tale.
Sharron Heginbottom, 43, Berkshire
For more information on lung cancer, contact the Roy Castle Lung Cancer Foundation