You've been an adult for 20 years? That would make you 38?
First, chill about the future. None of us can predict where things will be, we can only decide how we will react to change - change is certain. Most important, invest in yourself. Be the type of person that is resilient, flexible, and optimistic. The difference is that you see all that as a "fear factor" and I see it as the exciting world that awaits!
If it makes you nervous to think that far in advance, then don't. Focus on today, because that is all that you can control. You don't need to make any decisions about the future. Focus on your budget and saving/investing today. Then if you decide to have kids, you'll be in a good position for options, and then challenge your thinking. Do I have to move to the burbs to raise a kid - what if we didn't, etc. The difference is, if you prepare now, you'll have options and won't have to fret about the future.