What does it mean?

When a guy gets nervous when he talks to you & studders
Also I'm the only girl he says bye & hi too. 
I'm in school & he also waves Hi to me when he's leavin in his car, I feel like I'm in middle school, (&' I'm in college) that's what I don't get idk what's flirting anymore it's been too long since being single & I'm actually really liking a guy from afar bad crush but can't have the courage to talk to him I've never had that problem before 
Sorry but why can't I see all the replies ?!?