can I have a judge order I'm at the ob apt. an birth of my child

You can try. There is really no specific 'right' to 'being there' for a pregnancy. It's too vague, anyway. Do you have the right to go to her appointments with her, to be in the delivery room with her? Not specifically, no. But I have little doubt that if you assert your rights and it is proven via DNA test that you are the father, that you'll be paying child support.

You do have rights in this matter, and I am not trying to dissuade you from asserting them. I think you should. But for the sake of the care of your child, not for the possible purpose of forcing a reconciliation with the child's mother, or attempting to drive a wedge between her and her new boyfriend.

You mean for the delivery of the child I would assume not the 9 months to cook the kid??????????????????

To answer your question I do not think that any judge in the US at least would have the nerves to override the wishes of the mother to be, even if the person is her husband less alone an ex-boyfriend.

Even if you are the father a fact that can not be proven until after the birth you have zero rights until the child is born. Hell even a married woman can abort a child to be without her husband ok.

Next, I would not be signing any birth certificate until there is a DNA test done.

You don't say what country you are in, but I know that in Australia you have absolutely no legal right to be at any pre-natal check-ups, or to be present at the birth.
And given that she left you only a week ago and already has a new partner, you should definitely have a paternity test done as soon as the baby is born.