'Teen Mom' star Amber Portwood has been to hell and back.

The 24-year-old reality star has dealt with addiction, tragedy and a prison sentence, all in the public eye -- and all while trying to raise her daughter, Leah. Now, Amber is speaking candidly about her on- and off-screen struggles -- and how she managed to turn her life around -- in her new memoir, 'Never Too Late.'

"Honestly, writing the book was very therapeutic for me," Amber explained in a recent interview with PopCrush. "I did relive a lot of the emotions and the memories, but in a way it was good for me -- it felt like I was getting it out."

Still, it was no easy task for the Anderson, Indiana, native to recall some of the most trying times and difficult moments in her life, telling us that the hardest one to write about was the death of her baby sister.

Despite the painful memories, Amber kept writing -- not only for herself, but also because of her desire to help others.

"Know that it's never too late to change," the 'Teen Mom' star said on what she would like readers to take away from the book. "You have a choice in your life."

And she knows about choices. In February 2012, Amber made headlines for her controversial decision to opt out of court-ordered rehab and go to prison, where she served 17 months' time for violating probation and an illegal drug charge. While her choice raised eyebrows at first, it turns out that prison was the right option for the MTV star.

"I really worked on myself while I was in there," she revealed. "It kind of humbled me also. You don't have a lot of material things and you learn to live with the bare necessities. It was a frightening experience."

It's an every day struggle with addiction. Hopefully, one day it will get easier ... it's still really hard sometimes.

Frightening as it was, it gave Amber the time and structure to focus on her sobriety. (Amber has dealt with an addiction to opiates.)

"I was sober there, and I was in the CLIFF [substance abuse treatment] program and I learned a lot [about] anger management [and] learned tools to stay sober," she said of her time in prison.

Some of those tools? "I listen to music or drive to relieve stress. It's really good to go to twelve-step meetings, that's really good to keep you on track also," Amber said. "Each addict is different and they all have different ways of coping."

When asked if it's a struggle to maintain her sobriety, she was candid in her answer.

"Yeah, it is," the 'Teen Mom' star revealed, "but I have to keep reminding myself of all of the good things that are going on in my life and where I could be right now."

"It's an every day struggle with addiction," she added. "Hopefully, one day it will get easier -- and it has gotten easier since I've been out, but it's still really hard sometimes."

As she told us, one of the biggest encouragements to keep her sober is her family -- especially her daughter, Leah, who is now five.

"I see so much of myself in her," Portwood gushed. "She's so beautiful and she reminds me of everything I've worked for and why I'm doing what I'm doing, because I would never want anybody to go through the things that I have. She's just my reminder every day."

And enjoying time with Leah is a good incentive to stay sober -- because now Amber gets to be a part of her little girl's big milestones.

"She just started kindergarten a few weeks ago! It was so awesome!" Amber told us excitedly. "I wasn't there for her first day of pre-school, but I was so happy to be there for her first day of kindergarten."

[Leah]'s so beautiful and she reminds me of everything I've worked for and why I'm doing what I'm doing, because I would never want anybody to go through the things that I have.[/pullquotes]

As Leah heads off to school, Amber is planning for her own future as well, revealing that she is enrolled in college and will begin classes in the spring. She plans to study sociology ("I think it will help me understand people more") and later open up her own rehab center.

And, of course, she is currently filming for the upcoming season of 'Teen Mom,' which is set to air in 2015. While Amber couldn't give away any of the details about Season 5, she did explain what made her decide to film another season.

"I just felt like I'm in a different place in my life now and I'm a lot stronger," Amber explained. "I'm able to handle things better than I used to." That includes her relationship with Leah's dad, Gary Shirley.

"We're cordial," Amber said of co-parenting with her ex. "We're there for Leah, you know? We don't really have much of a relationship; it's just really point-blank for Leah."

And speaking of 'Teen Mom,' Amber couldn't contain her excitement for her 'Teen Mom' co-stars Catelynn Lowell and Tyler Baltierra, who recently announced that they are going to have a baby.

"Oh my gosh! I was excited for Catelynn because she is such a sweet, sweet, kind person and she is going to make an amazing mother," Amber gushed. "Tyler's going to be a funny and amazing dad."

And the 'Teen Mom' connections don't stop there. Amber will be embarking on a book tour with 'Teen Mom 2' star Kailyn Lowry, who is promoting her own memoir, 'Pride Over Pity.'

"I'm really excited for the tour! I feel like we're going to get to know each other on the tour a little better," Amber said of spending time with Kail. "And it's nice to have the two different stories, and I'm sure we'll help each other out with a lot of things. It'll be fun."

To pick up a copy of Amber Portwood's memoir 'Never Too Late,' you can head over to Amazon.