Why is my crush acting this way? (Sorry, it's long!)?

Hi, I've had a crush on this guy I met a little over a month ago and ever since he added me on Fb we've been talking every now and then (I would initiate the conversations, he did it once maybe). I've been going very slow and so far only wanted to be friends first in order to get to know him. I have spoken with him at school properly maybe twice only and I would greet him when I see him. So things were going very slow, I rarely see him but when I do, he always pretends like he doesn't see me and turns his back to me... While his BFF (that actually goes out of his way to be friends with me and also initiates conversations) will always greet me and sometimes even approaches me to talk, he doesn't. I remember noticing him looking or seeing me and then turning his back to me when he saw me noticing and that makes me pretty sad because many times I want to say hi... On Fb he said that he could help me with Korean and that it's not disturbing when I walk up to them and talk to them, but the things is, he "doesn't see me" at school? He is very confusing to me, even more today after I messaged him to check on what he thinks about a con I introduced to his friend which then told him about it, he replied that he was confused so I explained it to him and sent a link and all I got was "aaahhh D:"... Might seem childish but I can't help overthinking everything I get from him because he's very hard to approach for me because of his behavior... I actually walked up to him during lunch once and poked him so he wouldn't get away with pretending to not see me lol. Because even as friends, it's pretty rude to pretend to not see someone... Anyways, I'm wondering why he's acting like this? Why the change of attitude/response? What's he thinking? And what should I do? Should I give up?

Sorry its so long!
Why is my crush acting this way? (Sorry, it's long!)?
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