Portwood, who reportedly had attempted suicide before, said she never believed she was making enough progress.
"It wasn't just the program," she said. "It was the fact of being alone. It was personal. You know being alone, feeling like you're hopeless, you have nothing, feeling like an addict and you're never going to change, even though in your mind you're working so hard but every time you get to court it's not good enough."
She also said she wasn't comfortable with the way things have turned out for her, saying she "should have done more" with what she was given.
Despite that, she says, she doesn't regret her decision to spend part of her life behind bars, but acknowledged that it was a hard thing to do.
"You want to be free. Who doesn't?" she said. "But you know if you can't do it, if you can't do it, why are you kidding yourself?"
But she plans to make the most of her incarceration.
"I'm going to take some classes, I'm going to get my GED, take as many programs as I can. You know, just try to better myself for when I do get out and not stay in prison ... I'll be off the drugs, I'll have an education to get me a job, you have to think of the positives in this negative story," she added.
Experts, however, disagree with Portman's decision to forgo treatment and spend years in prison, saying that the decision to forgo treatment is just another in a series of bad choices for the young woman.
"I don't think she really realizes how severe a penalty she's choosing, when she could have worked outpatient in a drug program, gotten her GED, and also been allowed to take some parenting classes, so that she could develop a relationship with her daughter," Dr. Janet Taylor, a New York-based psychologist, said.
While Portwood doesn't directly blame being on "Teen Mom" for her problems, she said it played a role.
"Getting money at a young age, going to parties where drugs were given to you, that's what really got me. ... You make your own choices," she said.
The pressure that came with being famous, particularly having paparazzi camped outside her house for days on end, was hard to handle.
"It's like every time you go out to eat, you know, people are staring at you, talking, and it's hard," she said. "You get paranoid ... It's not normal, to always be paranoid."
Still, Portwood said she believes that she must keep going.
"I had been at such a low point, I couldn't go any lower," she said. "There's nothing lower than trying to kill yourself. That's why it's probably hard to understand why I did what I did.
"But when you mentally know that, you're not right. You're 22, and you tried to take your life twice. And you're 22, and you're still here, you don't want to mess that up."