Edited by dollface88 - 9/4/13 at 12:24am
WElcome to Mothering!!
THis sounds like a very emotionally draining situation!
He may not realize this, but you don't really have the right to say who he can and cannot introduce your child to if paternity has been established and you share custody, at least in most states. Unless the new person is criminal or has been established as dangerous by the court or mental health system, you can't really forbid contact. Even then you would have to petition the courts to restrict contact with the GF if she was in his life.
Is it possible you are using the situation with your child and contact with dad to try to get at him for the relationship? It sounds like both of you could use an objective family mediator or counselor to help you with the custody /visitation issues, and also a counselor to help you get over him, as it seems that he is not likely to change.