Why do I feel so strongly when I don't even really know the guy??

Okay so their is this guy that I just started to talk to this year. But we really haven't talked i mean we copy off of eachothers papers and we got eachothers back like he will get a book for me if i need it and i will do the same in return. We have talked a little but it really isn't much. And yet when today when i looked at his status he đã đưa ý kiến that he was with her and put like happy with a lot thêm letters then what was needed and that really hurt me and made me sad. That happens everytime i see him in a relationship with someone other then me hoặc something. I can't like the guy can I I mean he is cute i mean really cute but I don't know him like bạn should before bạn develop a crush so what is it??