I think it is natural to be afraid of it to an extent. And it's quite ok to wait until all parts of you are ready to get married and have kids if that's the path you choose. You can also get married and not have kids. Just take it one step at a time. If, as you say, you think your fear will lead you to miss out on opportunities that you want, I agree with trippin, talking to a counselor or therapist may help handle the fear.