On last night's premiere of "Teen Mom 2," we witnessed Leah struggle to regain the trust of her babies' father, Corey, and on next week's episode, life gets even more complicated for the young mother of two. When Leah notices that Ali is physically developing slower than her twin sister, she takes her to the doctor to be safe it's nothing serious. But the doctor doesn't ease her worry. "It's obvious there are some deficits," he says after a full exam, and Leah breaks into tears when she's told to take Ali for an MRI of her entire spine. We're all in for another emotionally charged episode of "Teen Mom 2"--check out the sneak peek here.