"My life has changed so much since I stopped doing drugs – my whole attitude has changed," Evans tells PEOPLE

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If the ladies from Teen Mom 2 know anything, it’s how to make it work when times get tough – and that’s exactly what cast member Jenelle Evans is doing.

The 23-year-old – who has publicly struggled with substance abuse, including a stint in rehab and several criminal charges – says she is finally sober and looking to the future.

“My life has changed so much since I stopped doing drugs – my whole attitude has changed,” Evans tells PEOPLE. “I’m more active in my children’s lives, and I want to be at every milestone and special event they have. Being there for them is more important to me than going partying or doing drugs.”

Evans says her children – Kaiser, 1, with on-again/off-again boyfriend Nathan Griffith and 5-year-old Jace from a previous relationship – are the ones who really keep her healthy and clean.

“Having Kaiser has kept me so busy and motivated that I don’t have time to hang out with the wrong crowd,” said Evans. “I only focus on my sons, school and my future.”

Before studying to become a medical clinical assistant, Evans dealt with plenty of ups and downs in her personal life. Shortly after getting engaged in January, she and Griffith decided to “break things off” to work on their problems, she tells PEOPLE.

Their relationship is known for emotional, explosive arguments that often end in police intervention – but to Evans surprise, the two “co-parented very well” during their time apart.

“It was my first time co-parenting with the father of my child because [Jace’s father] wasn’t in his life,” she told PEOPLE.

“We were both very understanding and very fair about the days that we had Kaiser,” said Evans.

The two have since reunited and are working things out together.

“In the end, he realized that he wanted his family back,” she says.

A new season of Teen Mom 2 premieres Thursday at 10 p.m. ET on MTV.