Hi Fox and the Hound, nothing really bad has to be going on in your life to be making you feel this way. Depression can just come from nowhere (although I do know you have been through some really tough times too....). The main thing is that feelings ARE there, and they are REAL!!
It is really good that you feel able to share them on here, but you DO deserve some help from professionals as well with this.
So do you think that you could start with someone e.g. a school counselor, your doctor........
There's no reason at all to feel worried, scared, ashamed, embarrassed.......(??) about telling someone. Just start by telling them what you've told us and take it from there.
We're with you all the way.
Alison