What can I do to stop feeling like a walking corpse?

I’ve just had my first real breakup with my first true love—I’m 19, she’s 18— and I keep blaming myself for how it ended, for what I could’ve done if I wasn’t so stubborn and blind. We both didn’t cheat or anything like that, we truly loved each other but we fell apart, and it didn’t help that we go to different colleges and only saw each other on the weekends when we would be free. It’s been a a few weeks and I can’t seem to get over her, I feel like a walking corpse, but it seems like she’s gotten over me. What can I do?