I can't show him the REAL me?

I'm 19, in a relationship with a sweet guy who really loves me. I do love him too, we're so attached to each other. But the problem is that I have the worst family life you can imagine. I just leant to keep my own sadness to myself, and when things get really bad, I just leave my boyfriend. I need some time alone to grief, but sometimes he can't accept that. He begs me to talk to him and open my heart, but I just can't. Talking about my problems makes me feel worse, it actually makes me feel very weak. Its hard for me to be with him at the moment, specially today when I had a big fight with my family. I even want to break up with him and just close the door of my room and cry. I have a torn family, literally. I'm depressed to the point that I don't wanna live anymore.