Jessica Simpson Reveals Her Baby Bump

12/30/2012 at 06:00 PM EST

Jessica Simpson is celebrating her pregnancy body.

The star, who is expecting her second child with fiancé Eric Johnson, shared a daring self-portrait of her baby bump on Twitter Sunday.

Dressed in a bikini and a beach wrap that is hanging open, Simpson, 32, writes "Bumpin' and Proud!" She snapped the picture with a glittery iPhone.

PHOTOS: Aloha, Baby! Jessica's Hawaii Holiday

Simpson has been posting lots of photos while vacationing in Hawaii with Johnson, their 7-month-old daughter, sister Ashlee Simpson – who flaunted her flat tummy in a barely-there bikini on the beach – and other family members.

The first picture Jessica shared with fans over this holiday was on Christmas Day: The image of her daughter wearing holiday pajamas and smiling in the sand atop the words, "BIG SIS," confirmed Simpson's pregnancy.