Ok me and my husband split in April, he got a heroin addict pregnant in June. She has already been proven unfit and has lost custody of her daughter to her mom. I took my husband back in August. I have seen the ultrasound pic. She is due in February. My husband does not want to fight for custody, as this Child's legal stepmother do I have any rights

Nope. You are not in any way related to the child and have zero rights to the child.

Your husband, however, is probably going to be paying child support to the child's grandmother (since she has custody), so you'd better start figuring out as a couple how you will budget that. Either that or convince your husband to file for custody of the child and then you can adopt at some point in the future.

as this Child's legal stepmother

Not sure what you think a legal stepmother is. A Stepmother is someone who marries a father with children. That's not you. But even if you were, you have no legal or biological connection to this child.

You are a step mother, there is no such thing as a "legal" stepmother. You have no rights what so ever in requard to the child