About my crush's behaviour.. (facebook)?

[Up]

Okay.. I'm pretty sure that he likes me as he shows all these signs in person.. Almost obvious..

But on facebook.. He sometimes replies within a couple of mins.. Sometimes a lot longer. He doesn't seem to try and carry on the convo.
i've only tried to start a convo twice. First ended in fear of annoying him. But a month or two later I was more sure that he liked me and I messaged him again. This was weeks ago now so I'm not expecting a reply.. I messaged him straight after he messaged me but he just never replied... (these are just silly inside jokey messages. Not important).

This would be fine and I'd accept that he was busy or didn't want to talk or whatever. But it still doesn't say seen even though he's been on facebook since.. He's not clicking this message on purpose... Why?

If I didn't think he liked me then I'd understand... But the way he is in person... He almost definitely does.... I don't understand....

Thank you!

[Mini]

first of all you should not take into consideration the things happening in facebook , it doesn't reflect the real feeling or attitudes of people , second if you really like him go and talk to him there's nothing wrong with that even if you initiate the conversation it's okey you have nothing to lose , and please over come the idea of annoying him .. if he doesn't want to talk to you he will tell you straight so pull away those negative thoughts