Heather Rae El Moussa is discussing the highs and lows she experienced while learning to co-parent with husband Tarek El Moussa's ex-wife, Christina Hall.

In a sneak peek of her interview with"The New Rules" on "Today," Heather Rae revealed it was a struggle entering a relationship with someone who had just gotten out of a significant long-term relationship, especially since he had children.

"I felt like I was always second, and no one ever made me feel that way, but I think when your significant other had such a long relationship with the previous spouse and a lot of love, and it was very public divorce," Heather Rae explained. "You’re coming into it, and you fall in love with each other, but you always kind of think of the ex."

When Heather Rae and Tarek got together in 2019, Tarek already had two children with his ex-wife and "Flip or Flop" co-star. Tarek and Hall share a daughter, Taylor, 9, and a son, Brayden, 4.

Heather Rae El Moussa and Tarek on red carpet

Heather remembers always feeling like she came second in her husband's life, admitting she couldn't stop thinking about his ex, Christina Hall. (Kevin Mazur/Getty Images for JBL)

HEATHER RAE YOUNG RESPONDS TO CRITIC WHO SAID SHE MADE BEING TAREK EL MOUSSA'S WIFE 'HER ENTIRE PERSONALITY'

Upon entering the relationship with Tarek, Heather Rae explained that she had to "navigate (her) own feelings along with falling in love with a man" while at the same time figuring out how to raise kids and continue filming her own show, "Selling Sunset," admitting "it wasn't always perfect."

"We definitely had some ups and downs, and they had ups and downs, and I think she realized how much I love the kids, and they are No. 1 to me over anything," Heather Rae explained. "So any drama aside, the kids are the most important thing to all of us." 

Heather Rae admitted taking on the "mom role" with Tarek's kids was a hard adjustment for her, because prior to starting a relationship with him, she was a single girl living in Los Angeles who "had time to be with (her) girlfriends" and was living with her best friend while filming "Selling Sunset." It was important to her not to lose that part of herself when taking on the additional responsibilities of a stepmom.

"All of a sudden, I jump into a mom role, a wife role, I take on his big family. I’ve always told my husband, my career is also very important to me, and I think that’s helped me maintain not losing myself. I take care of myself, I get my massages, I get my nails done, but I also am a really good mom."

Tarek and Heather El Moussa at MTV Awards

Heather Rae revealed she often has "mom guilt" when it comes to doing things for herself as a mom. (Amy Sussman/Getty Images)

While she works hard to maintain her sense of self, Heather Rae said she still experiences "mom guilt" every so often, explaining that while she is a "hands-on" mom, she isn't able to drop them off or pick them up from school because she has to film or is working on other things. She has, however, learned to cut herself some slack.

"Sometimes I feel guilty about that," she said. "Then I’m like, 'Why?' Because they’re happy, they’re healthy, they love me. I love them and I give them the time I have. And I prioritize them. So why am I feeling guilty?"

Heather Rae has been a stepmom to Taylor and Brayden since marrying Tarek in 2021, and she is about to become a mom to her first child, announcing she is having a baby boy on Instagram in July 2022. She often posts pictures of her family on Instagram.

Prior to announcing she and Tarek were expecting, Heather Rae opened up about her fertility struggles, revealing that doctors told her when she was in her 20s that she had a low egg count. This news devastated her, leading her to freeze her eggs in 2019. She told E News that she didn't think she would use those eggs until she met Tarek.

CLICK HERE TO SIGN UP FOR OUR ENTERTAINMENT NEWSLETTER

"Seeing Tarek with his kids really made me want a baby with him — because he is just such an incredible father to them," she told the outlet. "And, you know, I love watching them grow up in front of my eyes. … I started thinking, ‘Gosh, if I have this much love for them, how can I not have my own baby?'"

In a separate Instagram post in October, Heather Rae gushed about her stepkids, saying she couldn't wait for them to meet their new baby brother.

Heather and Tarek at MTV Awards

Heather and Tarek are expecting their first child together, announcing on Instagram they are having a boy. (Axelle/Bauer-Griffin/FilmMagic)

CLICK HERE TO GET THE FOX NEWS APP

"I couldn’t have asked for a better response from Tay and Bray about our pregnancy, and of course Tay was the very first person to find out because on the night I told Tarek about our pregnancy, we were tucking her in, and she said to us that if we do end up having a baby, she wants to be the first person to know … so we had to tell her right then and there instead of surprising her and Bray together," she said.