How to deal with stress?

the cuticle area around my right thumb is just destroyed. I'm constantly picking at it when I'm stressed or anxious and I'm starting to think that it's some sort of self-harm problem... my moms pretty worried about it too. I also have a pretty stressful week up ahead ( I've lost my second phone this year and my parents don't know, and I have finals) I know that my parents will love me even if I do dissapoint them, but lately I've felt like such a failure and I am constantly downing myself. How can I control these problems before they build up to something more serious? I don't want this to become some mental health issue