Breakup advice needed

guys i'm going through a really hard breakup right now. It's the first one where i was broken up with. We dated for two years and were unbelievably close. We basically grew up and became adults together. So basically he was still in high school and i was in college as a freshman and over time the relationship was becoming very strained and communication was hard. So he said "do you trust me?" and i said yes, and he basically said that we should go on a break until school ends and we can see each other again. Well now that school is over, he doesn't love me anymore and thinks of me just as "one of the bros." But i still love him so much. He's leaving for the marines for 4 years in August.  Do you guys have any words of wisdom for breakups? I don't know how to function without him. It feels like something is missing and going throughout my day with that empty feeling is so hard and i don't know how to get over it.