My family and I were on a trip to Legoland when we first started to worry about our son, Amarvir. He looked pale and tired. When we got home, we took him to the GP. It was September 2010 and he was six at the time.
The doctor did some tests to find out what was wrong but the night before the results were due, my wife Nikki and I could hear him crying in pain in his bedroom. When we tried to get him up to console him, he said he couldn't get out of bed. Then his eyes rolled back and he collapsed.
We called for an ambulance that took us to King George Hospital in Ilford, East London. They started doing more and more tests because they were worried about his blood cell levels.
At around 6pm, we were told he needed to go to intensive care. He was rushed to Addenbrooke's Hospital in Cambridge, with a police escort along the motorway. Nikki went in the ambulance and I had to drive separately - it was totally surreal.
Thankfully, our family were looking after our other two boys, Karamvir, who was five at the time, and our then five-month-old baby, Tejvir, so we were able to focus on Amarvir.
When we got to Addenbrooke's we were told that Amarvir had acute lymphoblastic leukaemia and septicaemia, and his organs were shutting down. They put him in a semi-induced coma to try to prevent brain damage and told us there was a 90% chance he would die that night, we should prepare ourselves for the worst.
It was so hard to know what to do in that moment. We were trying to take it all in while working out what to do next. They said we needed to say our goodbyes but we just couldn't accept that. We were crying, ringing our family and hoping the next bit of news would be better. We just couldn't think of the alternative.
Amarvir made it through those first 24-hours, then 48. By day three, treatment for his septicaemia was working, which meant he was able to start chemotherapy. It was such a relief to be past those first few days, but our lives had changed forever. We were told Amarvir was going to need at least three years of treatment.
The first few months of chemotherapy was an intensive course. Amarvir lost his hair, he was weak and he had to use a wheelchair. I gave up work for three years to care for him. After being told we could lose him, I wanted to do all I could and be with him as much as possible. We all knew we needed to stick together as a family to get through it.
Amarvir slowly started responding to treatment but there were many setbacks too, including infections. At one point his right lung collapsed and we had to go to Great Ormond Street Hospital. One day David Beckham came onto the wards to meet some of the children. Amarvir was feeling so poorly, he said he didn't want to meet him. He changed his mind a bit later and thankfully David was still there so Amarvir did get to meet him, but it showed how ill he was at times.
Amarvir is in remission now and is doing well at school. It's so wonderful to see him doing normal things, like a normal teenager. There are still check-ups and of course we always worry about him - if he gets ill with a cold or something. But he has been so brave, he inspires us too.
For my family, sharing our experience and talking about cancer is incredibly important. As Sikhs, there are cultural taboos that we want to break - we're totally open about what happened and we want to help others. And encourage others to get involved and Stand Up To Cancer with us.
I Stand Up To Cancer for my son and all the other children we saw on the wards. That's why next week I will be rowing five marathons in five days, kicking off in Chester and finishing in Liverpool. I want to do everything I can to help raise money and awareness. It's not going to be easy but I'm ready to take on the challenge and when times are tough I'll just think of my boy and how well he's doing today - it's remarkable.
We came so close to losing Amarvir and we'll never forget that. We never take life for granted anymore and are very proud of the man he's becoming. We owe his survival to the incredible advances that have been made in cancer research.
Jag is taking part in Stand Up To Cancer's Great Canoe Challenge. Stand Up To Cancer is a joint national fundraising campaign from Cancer Research UK and Channel 4.
The challenge is taking place from Monday 25 September - Friday 29 September. For more information visit: standuptocancer.org.uk/canoe, to support the Paddlers and donate £5 or £10 text CANOE5 or CANOE10 to 70404*, or donate online at standuptocancer.org.uk/canoe.