Somebody help...

I'm supposed to be at my mom's house for the day. I really don't want to start crying, because I won't be able to stop, and then she'll find me and ask what's wrong, and I don't want to upset her.
She just started talking about all this stuff going on in her life, like how her husband doesn't want me around my eight-month-old sister, but she doesn't think that's right because I'm her daughter, and how her decision not to keep me away is driving them apart... She thinks he wants out, because of me being at the house. But if I had known... I would have stayed away.
This happened three summers ago, when I lived at home, with my dad and step-mother. She left because he didn't want to give me up. He divorced her, and sold his beautiful house, and then two months after we moved, I got taken away anyway.
What if he leaves, because she doesn't want to let me go, and then I screw everything up like I did with my dad? I really need someone right now..