Why does my crush do this im so confused is his attraction growing/fading?

This is kinda long, but i really am desperate for an answer, please be honest
OK cool, so I joined a new school a few months back and there is a guy who i'm very attracted to who's been going there for a long time. Every-time he saw me, he used to stare at me lots, never talked, but just stared with his eyebrows raised if he saw me outside of class like inside our library or something (or if I was talking in class, sometimes hed suck on his bottom lip and also tilt his head). However, for some reason that's kind of reduced a bit and he doesn't really look at me lots outside of class.
He still stares at me like the way he does when I talk in class, you know by biting his lips sometimes and tilting his head (he doesn't really do it to other girls I've noticed) but he does it a tiny bit slightly less than before, he sits a seat away from me lol. However i kinda noticed he kinda indirectly responds to things I say or kind of talks to me i guess, it happened 3-4x in the past week, e. g. if I say who would use facebook anymore but hed react to that, by saying it out loud but not looking at me only talking to his friend, again he sits a seat away from me and his friend is in the middle of us.
Could it be that he was attracted to me, but kinda faded because I didn't really used to look or stare at him a lot, or sometimes I wouldn't even realise he was there so maybe he thinks I'm not attracted to him. Or is it because his attraction is growing more and he's trying to restrain himself. If so, how can I show subtle signs that I like him via body language, without saying anything because as I said before we never talk.
Why does my crush do this im so confused is his attraction growing/fading?
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