why won't he accept my friend's request on facebook?

[Serendipity]

So here's the thing; this guy and I are in school together and he is a year above me. The first time we met was in a group event where he asked me whether he would see me that night at the party; we didn't see each other that often except in club events etc.

when we talk, I feel that we have such a strong connection; he looked straight into my eyes, and had such a soft expression in his eyes. We literally stared at each other (without blinking) for half a minute until someone interrupted us. I think his pupil was dilated, because they changed color...He was standing really close to me and facing me completely. When I left, he gave me such a lingering look like he didn't want to break our eye contact.

I've caught him smiling at me and staring at me while we're both talking to other people. I feel that even though we don't know each other that well, and even if he doesn't like me, we're still classmates...so, why won't he accept my facebook friend's request?
I'd really appreciate your help! I'm so confused !