Kate Middleton
Kate Middleton has been suffering from a severe form of morning sickness - hyperemesis gravidarum.Getty

Almost six weeks after Clarence House confirmed the Duke and Duchess of Cambridge are expecting their second child, Kate Middleton is yet to make a public appearance.

Just like with her first pregnancy with Prince George in 2012, the 32-year-old royal is battling Hyperemesis Gravidarum, a severe form of morning sickness.

Because of her condition, she has pulled out of a number of royal engagements including the opening of Oxford University's new Chinese studies centre and Prince Harry's Invictus Games.

Her husband Prince William stepped in for her in the eleventh hour after she cancelled her solo trip to Malta.

Kate has been missing in action since 5 August, when she attended the poppy installation at the London Tower alongside Prince William and Prince Harry.

Feeling self-conscious?

However, a new report suggests that morning sickness may not be the only reason is she is shying away from the spotlight.

According to Inquisitr, the Duchess of Cambridge's non-attendance at high-profile public events is down to the fact that she is feeling self-conscious about her changing body.

Royal watcher Gregory Wakeman writes that the mother-of-one feels embarrassed and doesn't want to "show off her burgeoning baby bump and bloated features to the world as she continues to grow."

And just when it seemed that she had gotten over the worst of her morning sickness, she is said to be feeling worse than ever.

A source also tells the Daily Mail that after pulling out of a visit to her signature charity, London's The Art Room on 1 October and her visit to Old Portsmouth to meet with Olympic sailor Sir Ben Ainslie on 13 October, Kate retreated to her parents' home in Bucklebury, Berkshire so she can relax better away from the public eye.

She is said to be leaning on her mother Carole for support with dealing with her pregnancy woes, which have left her feeling useless and frustrated.

Although the Duke and Duchess are scheduled to welcome Singaporean President Tony Tan Keng Yam to London on 21 October, the palace has made it clear that her appearance depends on her health.

"Her engagements are being reviewed on a case by case basis," a palace spokesperson said of her notable absence.

"There will be engagements in October and November. We just haven't announced them yet."