I can give you my perpective.
Me and my ex-girl, we broke up 2 weeks ago. She was a very interesting phD i took, as i told her. In the past months she was a bad bad bad girlfriend, at least in the romantic department. I would care for her, massage, etc and I'm not the type of showing feelings. Now, if she talks to me for some reason, I treat her badly. I feel used, my heart is broken but i dont show it. For me, she doesnt deserve. If I show her that i miss her, I know she is going to think of me as a desperate guy and rejects me.
Well, i dont know what happened between you too, and i know its hard, but give it time. I've been there in that loneliness. No friends, no girlfriend, no joy, just empty, so, leave him be, and let yourself go. Its easier said than done, but there is no other choice, or at least for me, i dont have other choice.