Thank you for sharing your question with the Wefugee Community and sorry for the rather late reply!
I am not familiar with rules and regulations in the Netherlands, but as you are still in the asylum procedure, I am afraid that you will not be allowed to travel or leave the country in that period. In order to qualify for a family unification according to the Dublin procedure, you must have lived in that family unit already in your home country. Unfortunately, this is practical not even possible with an unborn child. As far as I understand the situation, you will need to apply for a family reunification visa at the German embassy. But I am not a lawyer, and I would definitely recommend you to seek legal advice in the Netherlands. I am sure you will find migration counselling centres which offer free services. However, I would suggest that you recognize the paternity as soon as possible. And as you are currently not able to travel to Germany, you and your girlfriend would need to do that procedure in the Netherlands.
I wish you all the best for you and your family.