Kate Middleton going through 'emotional ups and downs'

A former royal aide has revealed Kate Middleton's real 'worries and fears' during her battle with cancer.

Queen Elizabeth's former press secretary shared the truth about Princess of Wales' condition as she continues chemotherapy following her cancer diagnosis.

"She might be the Princess of Wales, but she is still a mother and wife and going through the same set of emotions and worries and fears as anyone else in that set of circumstances would be," Ailsa Anderson told PEAOPLE.

The 42-year-old put on a brave face during her first official public appearance in nearly six months at King Charles' official birthday parade, known as Trooping the Colour, in London on June 15. 

But, a source close to the royal household explained Kate's suffering in silence, claiming: "The treatment is punishing, and it is different for different people. And the side effects can be unforgiving."

Princess Kate, according to insiders, finds relief in the routines of daily life with her family, including children Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6.