Tom Stocky, a product manager at Facebook, took a four-month paternity leave from work to take care of his young daughter while his wife continued her job as director of product management at Google.

Staying at home with a 1-year-old was much harder than he thought.

"It was so physically demanding. You have to be constantly alert," the Menlo Park, Calif., man said. "She would find new things to try to eat, new things to try to stick her fingers or whatever else into. I mean … there were lots of dangers looming on all sides."

Another thing Stocky, 35, didn't expect? Criticism from stay-at-home mothers and others.

Facebook's Sheryl Sandberg Says Women Must 'Lean In'

"Why is there just insanely low expectations for me as a dad?" he said. "Someone's like, 'Oh that's so great that you're bringing your daughter to the grocery store.' But, then I was like, 'Well of course I am. Like, what else would I be doing?'"

Even though it felt nice to get a compliment for his parenting skills, he said it "felt a little insulting" after a while.

And when he used to take his daughter to music class in the middle of the day, he said he felt like he was "intruding … like I was impinging on this you know, existing mom circle. So I switched to one that was later in the day because that one had more dads."

During his leave, he said he learned a lot about the perceptions people had of fathers in general, and of women who stay at home.

"I think the expectations were very different for me as a father. I think they're much lower, he said. "Like if I change a diaper I get a standing ovation … I think the other thing, there's like certain preconceived notions, maybe, about, you know, what women and men are supposed to do. And it seems like there's some negative perceptions about women who decide to work full-time out of their homes, and men who decide to work full time in their home," he said.

WATCH: Sheryl Sandberg on How Women 'Sabotage' Their Careers

Stocky took to Facebook to vent about the negative perceptions, and he even started looking for groups for dads.

"They're hard to find," he said.

One stranger told him, "It's too bad you can't earn as much as your wife so she can be the one to stay at home."

Stocky's wife, Avni, took her maternity leave when the baby was born. Stocky said he took paternity leave in part because he wanted to reflect on what mothers go through.

"I just wanted to talk … have a conversation with people about what it's like to be an at-home dad and for the different challenges and nudges kind of pushing dads away from the homes and into workplaces, in the same way there are all these nudges that are pushing women away from workplaces and into the homes," he said.

At first, Stocky missed his job.

"But after two months … I started getting some of the benefits of all the work that I was putting in with my daughter. I mean, she liked me more," he said. "She would, like, smile and kind of light up when I was around. She would come to me for comfort. Those things felt really good."

Stocky got to see his daughter eating solids, rolling over and taking her very first step.

Today he's back on the job - he said he had a "pretty seamless return" - and is leading the launch of Graph Search , a new way to find people and places on Facebook.

"Now that I'm back at work, I miss being with her," he said.

Asked if he'd ever consider staying at home full-time, he replied: "I'm open to it … Nothing will replace that four months that I had a full-time with my daughter. That was amazing."