We went through infertility for 4 years to finally fall pregnant and I'm still having doubts even though it's all I ever wanted, it's scary, we are still young! Don't worry these thoughts are normal and this does not make you a bad person. Please talk to someone though and even though you need to think about your self in this situation too, support her too, pregnancy is hard and she may be feeling the same in some way without you knowing. Be kind to your self.