What is he doing?

My ex and I broke up almost 3 months ago. We were together for 3 years and had just moved out together. Before that we both lived at my moms house. We were both in agreement about it but he said maybe in the future we can work it out. We havnt really spoken except for the times that I've gotten his mail or got a call from his work. He re-added me to facebook a month after the break up, but doesn't start conversations. When I do go online, I see that he's on, then he's gone right away. This happens several times. I dont know what he's doing? I wanna be with him, but we broke up because of several things and I wouldn't go back if those things didn't change. I want to message him and tell him how I feel... but everyone says that if "he wanted to be with you, he would make the effort to message you". :( I dont know what I should do.
What is he doing?
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