Paternity test

why would my girlfriend of about nine years need to get a paternity test done before a boarding her pregnancy. I found out about the abortion about a month or so ago when she told me and eight fit of anger blaming me and my parents for the abortion I didn’t even know she was pregnant. I can only assume that another man was the father of that baby clearly she’s been cheating. Now she is nine weeks pregnant with I think is my child and I don’t know what to do we also have a five-year-old son.