Derek was rushed into hospital back in March and placed in a coma by doctors, and has remained in a minimum state of consciousness ever since.
The political adviser has woken but has limited consciousness and is unable to speak, and Kate has also revealed he has lost eight stone after the virus ripped apart his body.
Doctors have warned he may stay in his current condition, and Kate has admitted she is constantly terrified about what is around the corner for him.
The TV presenter, 53, has opened up about his health, saying her "heartbreak is very wearing" and that "there is more than the odd day when she is consumed with fear" about what is coming next.
She told YOU magazine: "Every issue I’m dealing with I automatically think, 'Oh, I’ll check with Derek' and then realise I can’t.
"There’s always this sadness. That and the heartbreak are the most wearing things."
She explained she sees Derek infrequently and not as often as she wishes.
Kate is looking after her children Darcey, 14 and Billy, 11, as Derek battles coronavirus.
She said she feels "ground down" and often thinks about the good relationship Derek had with her kids.
Kate added: "I’m always thinking how would Derek help Billy; he was so brilliant at all of that.
"I imagine all the conversations he’d be having with Derek – it’s heartbreaking to think they may never be having them again.
"If someone said to you, 'This is just a short-term period, you are going to get through it, then everything will get back to normal,' you’d have such a burst of energy.
"But it’s the same for anyone living with a loved one with Covid, it’s all an unknown. It grinds you down."
She added what she has to accept is she's "a de-facto single mum for now" when she's always thought "I don’t know how single mums do it".
The mum-of-two updated fans last month on Derek's condition saying he was receiving therapeutic plasma exchange (TPE).
Former I'm A Celebrity... Get Me Out Of Here! campmate Kate also admitted that she had offered to donate her blood to Derek several months ago.
While chatting with Dr Amir Khan on Good Morning Britain, she said: "I was looking for anything that I was able to do. But they said we are months away from being confident enough to clean your blood."
Derek was rushed into intensive care after being rushed to hospital and later placed in a medically induced coma.
Kate has updated fans via social media regularly as he battles the devastating condition.