Until paternity is established, either by agreement or by a blood test, she cannot force you to pay jack squat. (That's the Latin term, IAAL and LB.)
Paternity can be established AFTER the baby is born. If it's not yours, you're off the hook.
If it IS yours, you can be forced to help pay for the costs of the mother's health care and the birth expenses and child support for the child.
But things will remain in limbo until after the baby is born.
Yes, she can harass you until then, unless you get a restraining order.
Hope this helps!