dugong16,
i wanted to let you know that i can sympathize with you b/c i'm going thru the same thing. i've been married for 5 yrs. now and my husband is pushing more and more for children. we also discussed the issue before we were married... he knew i didn't want children and he said he was okay with that. now, he says he can't remember ever saying that; i think he believed i would change my mind.
i also worry about being old and alone, but that is not a good reason to have a child. there are no guarantees that your child will be there for you when you are older. i know it isn't easy, but you know what will make you happy, if that means not having a kid then don't! someone gave matt really good advice - it's better that you find someone who feels the same way you do about children than compromise, otherwise you and your husband will both be unhappy.
i'm not sure what will happen between my husband and me, but i'm not going to give in on this or i will resent both him and the child. it's not an easy decision to make, and yes i worry about the consequences of my decision, but at least i know i am being true to myself. besides, if kids are the only that will make him happy, i love him enough to want that for him - even if it is not with me.