ET recently sat down with the 29-year-old former Glee actress to discuss her new memoir, Sorry Not Sorry -- which hit shelves on Tuesday -- in which she gets extremely candid about her personal life. Rivera reveals in the book that she got an abortion six years ago, after she found out she was pregnant with her now-husband Ryan Dorsey's baby. Shortly before she found out she was expecting, she and Dorsey broke up so she could focus on her career.
Rivera says she "absolutely" still thinks about the difficult decision to this day.
"I think it's always on your mind, and it's one of those little scars in life," Rivera exclusively tells ET's Nischelle Turner. "When I was writing the book, it was really important for to include that, because this is ... a part of my story and a part of who I am. And like I said, the statistic is crazy -- there are so many women out there that are going through this and nobody gets to talk about it."
Rivera says there were multiple reasons why she decided to get an abortion. She likens the feeling of finding out she was pregnant to first hearing that her Glee co-star, Cory Monteith, had died. Monteith died in July 2013 of a drug overdose.
"It was a bunch of different factors, you know, and I was so young," she explains. "It was kind of that same feeling when I had the call about Cory, it was like the world stops, and you kind of black out for a minute. And you are like, 'What is going on? I have all this other stuff to do, you know?' So it was just never a real question."
These days, Rivera is mostly at piece with her choice.
"Like I said, it's something that is one of life's little scars that you get along the way, and the scars are never really healed," she muses. "They are always kind of still there -- they are just not bleeding anymore."
Rivera eventually married 33-year-old Dorsey in July 2014. The couple now has a son together, Josey, who turns one on Sept. 17. In her book, Rivera also reveals that she actually decided to tell Dorsey about the abortion only years after she had already undergone the procedure on a day off from Glee.
"That was really nerve-racking," Rivera recalls. "I didn't know how he would react, obviously. It had been so many years. He ended up saying, you know, one of the best things that any man in that situation could have ever said. And I think that it's just a true testament to him and us, and I'm grateful for where we are now."
Rivera, who previously dated her Glee co-star Mark Salling as well as rapper Big Sean, acknowledges that Dorsey has always been "the One" -- though she of course didn't see it at first.
"I have always kept a flame for him," she admits, referring to her feelings after their initial 2010 breakup. "In between boyfriends or whatever, if I was single for a minute, I would always answer his emails and go see him. He was just kind of always the One."
"When you're 23, you're like, 'There's gonna be something better out there,'" she adds about her previous mindset. "Trust me. Yeah, no."
Watch ET on Tuesday for more of our exclusive sit-down with Rivera.