He flirts with me, but then ignores me...?

[giganticnotebook514]

There's this guy in one of my college classes, and we've been talking for a while. He flirts with me so much - calling my hair pretty, gorgeous, saying I look nice, hugging me, sweet comments about my personality - and I like him a lot. we've got each others' numbers, but the thing is i don't have texting. And I'm not into social media, so no facebook, twitter, etc. I communicate mainly through email. I talk to him whenever I see him on campus, but that's it.

Is it b/c he's just not interested, or b/c he finds it hard to contact me, or something else...?
He also invited me to hang out w/him this past weekend at the library, but i told him i probably wouldn't be able to since my weekend was going to be busy. this was totally true. but did he perhaps interpret that as disinterest?
He's not shy...he's the handsome, popular, football-playing guy. everyone loves him, he's totally comfortable w/people. i'm more quiet, into music, books, writing, good grades. Also he's a senior, I'm a freshman.

How would I go about showing him that I'm totally comfortable w/him talking to me more often, without being all over him and running him off?