Am I Self Sabotaging

I have Been Slowly Building a close Relationship with A Girl over 3 years , We had a sleepover a couple weeks ago and I kissed her and we made out.
(She is a very goal oriented person works and Succeeds, she is a busy for understandable reasons)
But after our exchange of affection it seems there has a division between us.

I am Leaving For The Military very soon, and I was hoping to propose marriage to her before I left for basic training,
Yet with this division between I think I’m just going to withdraw my feelings from this relationship to avoid the heartache.
We Were have been very close and vulnerable with each one another, I have given my heart to her.
This Pains Me Because I thought I was playing my cards well, yet After My First Truly Romantic advances, there seems to have been a Stifle between us, she no longer reaches out to me or maintains communication over the via. telephone(text/call)
Should I explain to her how I truly feel, Or should I cut my losses and focus on myself.
Personally I think the best option is to zip it and forget it…
What could I have possibly done wrong?
What could I do ?
She Truly is once In a lifetime.
I feel so defeated.
Am I over thinking and self sabotaging?