On the dramatic 4th Season of Teen Mom 2 Leah, Jenelle, Kailyn and Chelsea deal with the ups and downs of motherhood, relationships, finances and careers. The girls face some of their biggest challenges yet, overcoming unseen obstacles and under pressure to raise their toddlers all while growing into resilient young adults. The last time we saw Jenelle she was struggling with probation and trying to turn herself around to be a better mom to her son Jace. Having met a new beau Gary, things seem to have turned around for her. But everything goes haywire when she finds out her new boyfriend had a past with her best friend. The couple patches things up, but shortly after they get into a dramatic fight that lands them both in jail. With Gary out of the picture, Jenelle turns her affections back to Kieffer and things spiral out of control as she battles with her mental health and drug use. Things in Leah's world are difficult as she deals with a miscarriage that leads her to question if she's moving too fast with fianc? Jeremy. When Corey tells her he still has feelings for her, Leah breaks off her engagement to give their family another shot at being together. But when Jeremy confronts Corey about the true nature of his feelings, Corey falters. Meanwhile tests show a possible new diagnosis for Ali's slow development, and everyone unites to support her. Kailyn can't stand Jo's girlfriend Vee, which leads to a violent altercation. She files a protection from abuse order against Jo, which forces the court to redefine their custody agreement. After Kailyn's boyfriend Javi moves in, she is forced to take a look at her anger issues when she lashes out at him. Javi decides to join the Air force. Working to heal her co-parenting relationship with Jo, they go to counseling, but Jo is not happy when he hears of Kailyns plans to take Isaac out of state to wherever Javi is stationed by the Air Force. Finally, Chelsea says she's over Adam, but reveals to friends a fear that she might be pregnant from a one-night stand with him. Chelsea also faces separation anxiety when she takes Aubree to day care for the first time so she can finally start beauty school. Chelsea is not happy when she discovers out Adam has a new girlfriend and she tries to move on but gets overwhelmed when circumstances force her to move several times. She decides to take a break from school to celebrate Aubree's birthday and her 21st, while finally settling into a new place.