My girlfriend is depressed and won't tell me what is going on, she just cries all the time, she just pushes me away ( think she's been hurting herself

I think you should just talk to her and try harder to get to talk to her even if she doesnt want to talk. Make her feel good about herself. If she feels depressed try to cheer her up by making her feel like you care about her. If that doesn't work, then you should tell her parents so she can get help.

You need to go to a trusted adult with this information and your concerns. Trust me. She could be suffering from some form of depression.