Jessica Alba said her husband was more like a roommate at times while raising their 3 kids

• Jessica Alba got married 13 years ago when she was nine months pregnant.
• She and her husband, Cash Warren, were committed to date nights, but in time that slipped, she said.
• Alba said she was growing alongside her family and keeping the lines of communication open.

After 13 years of marriage, even Jessica Alba struggles to keep the spark alive, especially while raising three children.

"It's all rosy for 2 1/2 years. But then after that, you become roommates," Alba said this month on Katherine Schwarzenegger Pratt's Instagram show, "Before, During, and After Baby."

"You're just going through the motions. You have the responsibilities. It's a lot of, like, checking the boxes, right?" she said.

Alba has been married to Cash Warren since 2008. They tied the knot when Alba was nine months pregnant with her daughter Honor, now 13. On the show, Alba said that Honor and her sister, Haven, 9, were both surprises, so she and Warren didn't have much time to adjust to married life. They had planned to have their son, Hayes, 3.

At first, Warren and Alba were good about doing weekly date nights where they didn't talk about the kids or the to-do list at home - but with time, "that stops, because of whatever," Alba said.

Though they don't have date nights as often, Alba said, she and Warren still pay attention to the way they talk to each other. They focus on "being able to communicate when you're unhappy and nipping it right away instead of letting it sort of fester," Alba said.

Alba said she sometimes takes for granted that Warren will be there.

"We have, like, obviously the friendship, the comfort of, like, 'you're not going anywhere,' and so sometimes you don't treat those people the best, right? You don't consider their feelings in the way that you would consider other people's feelings," she said. "So that is something that I think is a constant one to work on."

Alba said she definitely didn't have all the answers to a happy marriage. "If you've figured it out in your relationship, let me know," she joked.

Alba said her biggest surprise in motherhood was how she'd had to become more comfortable being vulnerable. "I feel like I didn't really understand the nooks and crannies of the complexity of feelings and relationship dynamics," she said, adding, "There wasn't a lot of space held for vulnerability."

Since becoming a mother, Alba has realized that she can still be strong and successful while also being emotional, she said.

"Instead of vulnerability being, like, a weakness, it's actually a strength," she said.