Called mother twice

I called mom twice today, and both times, she hung up on me.

I am suspecting that she was angry at me not calling her often enough during this past month. But I am also suspecting something else being wrong, which I don't know what it is. I don't know what to do. Last time when I called her, she asked:"is there anything you need to discuss with me?" I said no. She didn't see to want to talk to me very much. That phone conversation lasted for about 4 minutes and half the time it was filled with silence.

I feel paralyzed right now.