The TV presenter's husband, 53, was rushed into hospital on March 29 after his condition deteriorated whilst battling the killer disease, and was soon placed into a medically induced coma.
Kate has recalled the first time she got to see him in weeks was on a FaceTime call while he was unconscious in his hospital bed.
She told YOU magazine: "When I finally got to FaceTime him, seeing him unconscious was a big shock. He’s lost nearly eight stone in weight, a lot of it muscle throughout his body.
"He looked worn-out,thin and pale with dark circles under his eyes and there were lots of tubes."
A heartbroken Kate also wasn't allowed to visit her husband in person due to restrictions, and his kids still haven't been allowed to see him.
Kate revealed on GMB that the medical team looking after Derek told her that his eyes appeared to respond when they put her presenting on the show on his TV, meaning there are small improvements to his condition.
But Kate has admitted she has no idea whether his condition will ever get any better, saying: "We hope and believe he will come out of it, but we just don’t know.
"The heart of the family has been ripped out and we don’t know if we will ever get it back."
She added: "If they say this has improved today you don’t feel the euphoria you’d like because you have this feeling the next day something else will have gone wrong.
"At first it was all about Derek’s lungs, but then his kidneys started failing and he was on dialysis. Now they’ve realised Covid can affect every cell of the body."
Kate also revealed that doctors told her that Derek was the sickest patient they'd ever treated who had managed to survive for so long.
Whilst he no longer has coronavirus, the damage done to his body has been so extensive that doctors aren't able to give him a full prognosis, leaving Kate "consumed with fear" about what is around the corner for him.
Kate has since returned to working on GMB and has been looking after her two children with Derek, Darcey, 14, and Billy, 11.
She took a break from the show to help her children get ready to get back to school, and whilst Derek's condition has only slightly improved in recent weeks, she is trying to remain optimistic.
Kate finished to YOU: "What you have to keep thinking is there were so many moments when doctors thought we’d lost Derek or were about to, and he’s still here. There is still hope."
The couple had been planning to renew their vows this Thursday, after Derek re-proposed to his wife as he admitted her stint on I'm A Celebrity in 2019 "made him fall in love with her all over again".
GMB continues tomorrow at 6am on ITV.