Someone release me from this god damn depression?

Don't listen to what anyone says about you, they have no soul. Your sister is picking on you because she probably has some problems of her own, and this is how she's expressing it. I'm glad you have somewhat of a grasp on your religion that is preventing you to do anything horrible. You need to know that you are valuable to someone, even if you don't believe it. You have so much more of your life to live. College will be totally different, I promise.