Bec captioned, 'Just packing up our house and found this. I mean, no wonder I got all the fellas when I was 15.'
'Ps. Hey @jaredleto,' she added – referencing the Jared Leto poster on the wall behind her.
Now, Bec is known for her glamorous lifestyle. But, despite that, the model is never afraid to share the realities of motherhood.
Earlier this year she released her first book, The Baby Bible, filled with expert advice and tidbits from her own experience parenting four children.
Back in May Bec opened up about the struggles she faced with breastfeeding and the horrible engorged breasts she experienced following the birth of her eldest son, Oscar.
Describing the pain as 'excruciating', Bec says: 'I was a blubbering mess for two days with these bloody boobs. To touch them was like touching a wall. They were rock hard. It was awful. They were boiling hot. Burning hot.
'I was skinny arms and legs and bazookas out to here.'