The singer had posted a group photo of herself on 16 August with her English record company, explaining that she’d played them her whole album.
And later on she shared another photo of herself posing for a selfie in the mirror with the caption: “And now this.”
Pink shared the topless photo showing her fans she was pumping milk, and used the hashtags #pumpupthejams and #mumbreak.
Pink, who gave birth to her second child Jameson with her husband Carey Hart in December 2016, is also mum to five-year-old Willow.
“As a pumping mama myself, I know it’s not easy,” one person wrote on the photo. “You’re an awesome lady for your fans to look up to. Keep on keeping on, mama.”
Another wrote: “Amazing. Another reason to love you except for you being an amazing singer and musician.”
And a mum also commented: “It’s not easy to be a pumping mum. I adore you Pink. Thank you for being an amazing role model and mumma.”
Pink has shared several shots of herself breastfeeding since giving birth to her second child. One photo that received praise was a snap of her breastfeeding Jameson while cuddling Willow.
“So beautiful,” someone commented on the photo at the time. “Never felt more alive than when I was nursing my babies.
“I had them both with me at all times too.”