Why is my mother this way?

Since I can remember, my mother's love has never been unconditional. If my sister, brother, and I didn't do things exactly as she wanted us to, we got the silent treatment. As we became adults, she wouldn't talk to us for months over what she misunderstood. I've done my very best to include her in my life and the lives of my two children. I've gone out of my way more than most people would to help her and do what I know she likes. I have a new niece and I've driven all over the city getting relative's clothing for her, using up tanks of my own gas. I have tried so much and I thought it was going really well. We hadn't gone through that in months. Today I am down with the flu and have been for the past 4 days. My Mom on the phone yesterday said she felt sorry and wanted to take the kids from today until Sunday. THen she had trouble at work and when I called her to ask her how she was feeling, she went off on me. I don't know why. She then said she had no sympathy for me.