The former TOWIE star, who already has daughter Nelly, 2, with Greg Shepherd, took to Instagram today (18 September) to announce the happy news -and she did it in a super cute way!
In the adorable snap, Billie can be seen wearing a sarong and pink bikini, revealing a glimpse of the beginning of the bump, which Nelly is pointing to. How cute!
Smiling about their new arrival, both Billie and Greg look down at Billie's stomach, while Greg holds Nelly and has an arm round his partner.
Pretty adorable, right?
Alongside the super sweet photo, Billie wrote "...And then there were four" and added a baby and love heart emoji.
A rep also confirmed the news to the Daily Mail, stating: "They are all extremely happy."
Billie's currently sunning it up on holiday with her family and earlier in the week she showed off her gorgeous collection of bikinis in an array of envy-inducing snaps. Who even knew she was pregnant at the time?!
Billie gave birth to her first baby Nelly, on July 9, 2014, and the cutie has made various appearances on TOWIE since being born.
Earlier this summer, Billie bowed out from the reality TV show after a whopping nine years, no doubt to concentrate on family life now there's a new baby on the way.
In the past, the Essex girl had made no secret that she was keen to be pregnant again, and told Reveal she hoped to be " pregnant by the end of the year".
She admitted: "It's still in the plan. I am trying because I would like to have another baby soon.Obviously you can't exactly schedule it. It happened really quickly with Nelly, so I'm just going with the flow."
Billie had also revealed that they often asked Nelly if she'd like a sibling, explaining: "Me and Greg always go to her 'do you want a brother or sister' and sometimes she says, 'brother' and then sometimes she says 'brother and sister' and I'm like 'she wants more!'"
Aww, well Nelly's got at least one on the way for now. It also means that baby Paul - Sam Faiers' son - will have a new cousin to play with.