Mixed feelings....

(sigh) All of the sudden, all the feelings came back. I thought I was past that portion of my life. I had already convinced myself that I was over him, but apparently, I'm not. I really do miss him, and I hate myself for it. I already told him that there could no longer be an 'us'. I'm so alone in this world, and he was there to be lonely with me. Now that he's gone, I want him back (4 months later). What am I supposed to do?