"I'm really ashamed and embarrassed with the things I said," Bynes told Paper Magazine. "I can't turn back time but if I could, I would. And I'm so sorry to whoever I hurt and whoever I lied about because it truly eats away at me. It makes me feel so horrible and sick to my stomach and sad. Everything I worked my whole life to achieve, I kind of ruined it all through Twitter. It's definitely not Twitter's fault — it's my own fault."The former child star, who rose to fame in the '90s on shows like Nickelodeon's "All That" and "The Amanda Show," said she's been sober for four years and is currently enrolled at the Fashion Institute of Design and Merchandising.In 2014, Bynes was sentenced to three years on probation, an alcohol education course and paid a fine after entering a no-contest plea to reckless. She continued to make headlines that year for a series of shocking tweets that included false accusations of abuse against her father."Everybody is different, obviously, but for me, the mixture of marijuana and whatever other drugs and sometimes drinking really messed up my brain," Bynes explained. "It really made me a completely different person. I actually am a nice person. I would never feel, say or do any of the things that I did and said to the people I hurt on Twitter."Related: Amanda Bynes' bipolar diagnosis turns murkyShe said the combination of marijuana use and a shift in her schedule contributed to her spiral."I just had no purpose in life. I'd been working my whole life and [now] I was doing nothing." Bynes continued. "I had a lot of time on my hands and I would 'wake and bake' and literally be stoned all day long … [I] was just stuck at home, getting high, watching TV and tweeting … I never did heroin or meth or anything like that but certain things that you think are harmless, they may actually affect you in a more harmful way." Around the same time, following a psychological evaluation and hospitalization, Bynes tweeted — and later deleted — that she had been diagnosed with bipolar disorder. In the Paper interview, she said she does not have a mental illness. "It definitely isn't fun when people diagnose you with what they think you are," Bynes said. "That was always really bothersome to me. If you deny anything and tell them what it actually is, they don't believe you. Truly, for me, [my behavior] was drug-induced, and whenever I got off of [drugs], I was always back to normal. I know that my behavior was so strange that people were just trying to grasp at straws for what was wrong."Bynes said she hopes release a clothing line and eventually get back into acting. She also hopes her experience will serve as a cautionary tale for others. "Be really, really careful because you could lose it all and ruin your entire life like I did," she said.