You are what is called under the law the "putative father,"  meaning that you are the supposed father of the baby.  Now you have to establish that you are the father of the baby.  That is generally done through genetic testing once the child is born.  Once you assert that right and your parentage is confirmed, your ex can not give the baby up for adoption with out your consent unless she has your right terminated.  Terminating parental rights is not an easy thing and it doe not sound as if there are grounds here anyway.  So if she does not wish to have custody of the baby then maybe you can obtain custody.  I would seek legal help here.  Good luck.