Depression

When one thing happens everything seems to come crashing down. That's how i feel anyways. I have been temporally placed in a foster home. I didn't feel like a stranger, they welcomed me with open arms. I have always been a happy go lucky kind of girl. Very sensitive, loving, kind, a girl with big dreams. When i look in the mirror now i see a dark, insecure girl, who cries almost every day of her life. I never thought depression would take over my life, but it is right at this very second. I wake up and throw on a fake smile, but that's determined on what kind of day I'm having. Most days i wake up, debate on getting out of bed, Get ready for school, Go to school, come home and sit in my room. I only come out when i have to use the bathroom and for dinner. I don't really have that big of an appetite anymore. I have sat in my room non stop for three days straight now. I have caught myself getting comfortable and sleeping, even if I'm not tired. I don't have the urge or feeling to do anything anymore. I don't see myself amounting to anything anymore. All this  coming from a girl with big dreams? I am at the point of giving up all hope. How can this be the life for me? How do i over come this depression? Why did this have to happen to me? I have all these questions i would like to ask but who do i ask? Do i tell my doctor? My counselor? My foster parents? Family and friends is out of the question! I have been hiding this from all of them because i wasn't ready to tell myself. I thought if i could get high or drink a little something then all this would go away, maybe that's where this problem first started? I'll never know. I know that dealing with this will be the hardest thing i will ever do. As of right now i have no energy or strength to do anything. I feel so lost and helpless. I am a complete mess, I have fallen apart, tried picking my self back up but it feels like as soon as i start feeling good again something happens and i fall back down again.. I need to get help.. Where do i start?