depression: someone to confide in

I've had depression my whole life. I've been doing better lately but this morning I woke up and I felt the saddest I'd ever felt in my whole life. All I've done today is cry and lay around, and I made a cake late at night to say I did something tangible. My body physically feels empty. I hardly eat. I want to throw up to get the sadness out. It's the weirdest thing because I've been doing so good and today everything was awful and I have no hope and I am so afraid I will feel like this for my whole life (I can't do that). I so frustrated because I don't know why I'm sad. 
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My biggest problem is, I have literally no one to talk to. I have 3 close friends, 1 I cannot talk to because we run in different circles and she does not know the friends that I have problems with usually and the two others are growing closer and leaving me because I do not do drugs. The latter 2 just got back from a trip with some of our other friends that they are now very very close with, which makes me anxious. I don't have a boyfriend to talk to and I do not make friends well (idk why I must have a bad personality). My sister has really bad mental problems so I cannot confide in her. Someone please please help:)