Welcome Melissa!
My SO and I recently got engaged and have similar concerns to you, you're not alone.
I wouldn't want to be with any other man, but the uncertainty and schedule can be tough to deal with, especially with us both wanting to continue our careers and have a family. We haven't come up with a solution yet, but we're hoping it'll all work out.
This is a good resource to help get a good idea of what to expect though - welcome again!