We had Ofsted in and I was doing an A-level PE lesson outside when I started to feel like I had a dead leg. Underneath my tracksuit I could feel a golf-ball size swelling at the side of my knee, but I couldn't remember knocking my leg or doing anything that might have given me a bruise. I mentioned it to my colleagues and they advised me to see my doctor. I did that afternoon, had a blood test and was told I would get the result in a week.
The next day we had a rugby match after school. I came home late and there were several missed calls from my doctor with requests to call immediately. The surgery was shut by then so I waited until morning.
The next morning the doctor phoned and told me to go to the hospital's haematology department quickly.
I had been told to ask for a Dr White. When I arrived I was told she was in the Macmillan unit. The word Macmillan immediately translated as cancer and all sorts of things went through my head.
When I found Dr White she started by apologising that I had found out I had some sort of cancer before they had had a chance to speak to me. Then she told me I had chronic myeloid leukaemia.
I felt shell-shocked. I had heard of leukaemia, but I didn't know much about this type. The first time I started to feel any emotion was when I had to phone my mum to explain what was going on. I left the hospital and remembered that I had switched my phone off, so I turned it back on and there was a message from Mum saying: "The hospital phoned, what's happening?" I called her and broke down.
Dr White said time was of the essence. It was 10.30am on a Friday, St Patrick's Day, and they had to get everything done before the weekend. Later that day I had a blood transfusion and I was finally able to discuss my condition properly.
The treatment started immediately and I was off work for a month. I was one of the trialists for a new drug that reduced the need for chemotherapy. Before the pills came along the normal course of treatment was a bone marrow transplant. They tend to use that as a last resort now.
When I returned to work full time I continued as a PE teacher for about a year. But running around and refereeing football matches proved too much.
Eventually I went to see the head and asked if there was a position elsewhere in the school. My second subject is maths and I also love music, so they gave me a half-and-half timetable mix of maths and music. After a while the head of maths requested I teach maths full time.
A few days after I was diagnosed, our school basketball team was in the county basketball finals and the head of PE invited me to go along and watch even though I had just started my sick leave.
On the minibus driving to the finals, he mentioned the idea of fundraising. I knew fundraiser concerts were a good way of making money so I got to work planning one for that summer. It featured a lot of acts and my own band, Breathless, headlined. We have held the concert every July ever since. So far we have raised over #163;8,000 through the concerts, sponsored walks and my solo album. This month I joined Sir Ian Botham on his Forget-me-Not walk in Milton Keynes.
I'm 38 now and it is four years since my diagnosis. With the way I'm being treated remission is not an option; the condition is managed with medication. The doctors tell me that with my numbers - the blood count and the leukaemia count - on this course of treatment, no one has ever deteriorated. It's all looking good for me.
Ed Jones fundraises for Leukaemia Lymphoma Research. Visit www.llresearch.org.uk. He was talking to Shade Lapite.