The model mum of five told her followers the news on her Instagram Stories.
She shared a picture of herself FaceTiming a smiling Harvey.
Harvey, 17, suffers from Prader-Willi Sydrome, a genetic disorder which can lead to behavioural problems and learning difficulties.
Sharing the screenshot, Katie revealed she was missing her first-born.
Always hard being away from Harvey in the week when he's at residential.
She said: "Always hard being away from Harvey in the week when he's at residential."
Katie added: "Thank God for FaceTime."
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Harvey spends weekdays at the facility before heading home to spend the weekends with his mum and his younger siblings.
Last month, Katie shared a clip of Harvey pleading with his biological father, footballer Dwight Yorke, to get in touch and get to know his son.
In the video, Katie asked Harvey who he wanted to "write a message to on Instagram".
The teenage replied: "Daddy Dwight. I love you Daddy Dwight, you look beautiful."
Katie has recently returned from performing at a garage festival in the French Alps and has announced she is set to release her new single "soon".
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