The 34-year-old singer, who already has two-year-old daughter Willow, fuelled pregnancy rumours after she was seen with a tiny baby bump while jogging in LA earlier this month, reported Ace Showbiz.
During the couple's recent shopping trip, Hart was seen caressing her apparent bump.
"They were cuddling and he kept rubbing her tummy. She was quick to move his hand away in case anyone saw. But it was pretty obvious," a source said.
Pink previously revealed that she wanted a big family with Hart.