If thats the case, I really think your DP should reconsider putting his name on the birth certificate. He won't need to adopt the baby officially for you to change the name (my ex's name was changed at 10), again, your child can have any name you want, but it would make life easier in every way if you were to put your DP down as the father.
Also, you can just leave the name of the father blank on the birth certificate. Women do fall pregnant unexpectedly without really knowing the father to be able to put details on it. You don't need an affidavit for those situations.
If you did it now, nothing would need to be explained to centrelink, CSA wouldn't need to get involved & you won't have to do all that paperwork later on.
Does your DP still consider this his baby, even though he's not the bio father? Maybe you need to talk to him about this. If you two were to seperate down the track, would he still have a relationship with the baby? It seems because you guys went through other measures to conceive, that he really doesn't feel as though its his child & I think you really need to address that now. He needs to commit in full now, before the baby comes. A father is the person who loves & raises a child, not the person who supplied the DNA.

