WHY AM I SO FUCKING DEPRESSED

I've been depressed for a long time now and went to get diagnosed about a year or two ago and I have no idea if I'm depressed over the same shit. But I just feel so alone and I have idea what to do. I constantly cry for no damn reason and I just want to end it all but I have no idea why. I can go on with my normal life but I breakdown constantly. I feel like I'm missing something or maybe it's the fact that my mom holds me responsible for everything my little brother and sister do. It's like I'm their mother.