Revealing the truth

Today I was at work and I was talking about how much i enjoy being around little kids and one of the women I work with said, "Nancy you need some grandchildren."  As I was walking around setting up the room I said, " I do have grandchildren but I don't get to see them, because my daughter doesn't like me very much."  I didn't look at her, or make eye contact, and I said it in a very glib way, but it hurts to say.  I never really know what to say.  I always feel very ashamed.  What kind of person does not get to see her daughter or grandchildren?  I don't know if I should ignore people or if how I should handle this situation.  I know that it makes people feel very uncomfortable.  My mom called yesterday.  I can't bring myself to call her back.  She sees my daughter and keeps everything about her a secret from me.  I just can't bring myself to talk with her, and it weighs very heavily on me.  Sorry,  but today isn't  a good day.