Thank you for your question
My name is ***** ***** I shall do my best to help you
Your ex can indeed register the birth without your name going on the certificate
However this doe snot mean that it cannot be added later - nor does it mean that you will not have a relationship with the child.
the law says that a child is entitled to contact with both parents and the courts will enforce this if necessary
You should try and discuss matters with your ex using Family Mediation
If that fails then after the baby is born you will have to make an applictaion to the court for a Child Arrangement Order
Please ask if you need further details