Custody for Single Mother, Virginia

[Stephanie313L]

I don't know how to go about filing for custody. If I am to file for custody and he doesn't abide by the agreement, what happens to him? I've come to this decision because my sons father is inconsistent and unreliable, creating an unstable/unstructured life for my son. I don't think that it's fair for him to be able to make a schedule on his own or to inconvenience my son and I anymore then he already has. He doesn't pay child support and he doesn't even have a place of his own. I feel terrible leaving my son with him but on the other hand I feel terrible about taking him away from his father. Suggestions?