My young friend (and I don't say that condescending, but only b/c I'm 34 and had my heart stuffed a couple of times when I was younger), I agree with these others...it is time to move on.
At least for now. Let this young lady go off and do her own thing. If she misses you enough, she'll come back. Right now, she's not missing you at all (I don't care where this guy is headed off to in the Army).
I'm impressed that you seem to be a guy who takes relationships seriously. Many guys do not, and its too bad. But, in this case she isn't taking the relationship very seriously, and is not committed to you (not enough).
You're better than that, and I hate to use this worldly phrase, but you deserve better.
Maybe taking some time off from dating would be a good thing for you. Go to a Stars game, go to SpeedZone. Grab some "guy friends" and go watch an action flick. Don't let your hands sit idle, or your mind will wonder too much and you'll miss this girl way more than she deserves to be missed right now.
I'd say, "You want to date other people? Fine. Let me know when you want to get serious. You know how I feel about you, and its time to reciprocate that. If you can't commit, I understand. C ya."
Sounds harsh, but the only way she's gonna know if she cares about you is if you let her go do some other stuff right now for awhile. And if she comes back, it should be all or nothing, IMHO. None of this wishy-washy stuff.
Take care of yourself.
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