Help questions on custody and support?

ok my ex girlfriend decided to move in with her parents and go after me for child support and she doesn't want to let me see my kid at all. is it possible to ask the judge for 50/50 custody i love my son a lot and its not right that she tells me i cant see him since I've been supporting the both of them till about a month ago i still buy dippers,food and clothes for my son but there not staying here anymore