Lost, "invest" in really good (really good) birth control, and use it every stinking time. That's the best guarantee you have for being able to afford children later. If you have them right away you will likely be financially screwed for a long, long time. School is really hard when you have little ones waking you up all hours, many people can't hack school, job and kids all at once.
Military hmm? How do you guys feel about being away from each other for boot camp, training and then wherever you are stationed. What if the gov't decides they don't need any more medics right now and wants to send you into combat? I think you are smart to be thinking about what you want, and what the alternatives are.
And like a couple other people pointed out, kids are way more expensive than just the pregnancy/birth. Those costs are a drop in the bucket compared to the hundreds every month for kid stuff. Besides, what about going out, socializing, hearing (or playing) music, seeing movies, and all the other stuff kid-less people actually can do with a little spare cash and a little time?
Keep thinkin', you're doing good...
Odrade