Asked how she felt when she found out, she told Enable magazine: "Devastated.
"This beautiful looking boy in my arms that couldn't see, move much or eat...
"I was worried about the future, but with the support of my family, like others who have gone through this too, you get through it and the pessimistic view can become optimistic... gradually."
Harvey, son of former footballer Dwight Yorke, is now nine years old. He has septo-optic dysplasia, which has affected his eyesight, as well as behavioural problems, autism and mobility difficulties.
Katie opened her heart to raise awareness of parents with disabled children and to ensure her son – and children like him – have the best opportunities for education.
Celebrity Mum Of The Year Katie, 33, who also has children Junior, six, and Princess, five, by Peter Andre, said it was vital for parents to pluck up the courage to challenge doctors about their decisions.
"After support from other parents in the same position as me with their children, they gradually gave me the courage to question the doctors," she said.
"You become a kind of expert, then you ask for more support. You realise you have to push for everything for your wonderful child.
This never stops and never will stop. My son is entitled to the best I can offer him and this is the same for every parent of a disabled child – it's their entitlement.
"Don't just sit there and accept what is offered to your child, get together with other parents and fight."
Katie said she has now submitted an application to create a new Academy for Harvey and his classmates after they had to leave their current school – which was designed to maximise their ability to learn – because they are too old.
She said: "Having disabilities is hard enough, let alone going to another school starting with new children.
"Harvey has known his classmates since he was a year old. We want to cater to visually impaired children and young people who also have special needs aged between five and 16.
"After this age we want to ensure these pupils can continue to remain in contact and meet each other so we intend to set up a club for them too. After leaving school these children are often forgotten. With us they won't be."