If you have signed a voluntary placement agreement with CPS but the father hasn't - AND the father is on the birth certificate - then arguably the placement agreement doesn't apply to the father and he should go get the child. He's the dad (if he's on the certificate) and he has a constitutionally protected liberty interest in parenting his child. If CPS is serious about this placement then they need to be sure they have done it properly.
You want to be sure to always be looking out for your child's best interests, not the dad's or yours. You are parents. You can - and should- deal.
You need to play really nice in this particular scenario, ask for services, utilize services, be clean, provide UAs on demand without complaining, take parenting classes and demand your visit time. Don't bother arguing with your mother - it is the CPS caseworker you have to charm.
Hope this helps. Elizabeth Powell