Exasperation one minute, enthusiasm the next. What's he doing?

For the past few months a guy and I have been having what I can only describe as a staring contest whenever we're in the same room. We've been friendly in the past & when I started feeling sexually attracted to him (because of his intense staring, and smiling when we did talk which gave me the impression he liked me) I got shy and I find it hard to talk to him anymore. I barely acknowledge him first, we only talk if he initiates the conversation which he's doing less and less and now it only happens when I'm with another person. He'll make a point of talking to them and doesn't make much eye contact with me, yet he can do it from a distance. Today when our eyes met across the room, he looked straight at me and looked away exasperated. I thought that was a clear sign he's tired of my BS (ignoring him because I am crazy about him) or entirely dislikes me and would rather avoid me from now on. So I leave the room, pretty satisfied that his expression was my answer.

Then 20 minutes later, I'm outside getting into the car while talking to a friend and he's walking to his, his head turned to the side, genuinely smiling at me.

Then I couldn't figure it out, he acts like he hates me then he's friendly. He could have just walked to his car, it's not as if looking in my direction and acknowledging me is unavoidable. I'm not sure what happened between the look in the room and the smiling outside. Guys, if you're into a girl & she's not paying you attention would that be something you reacted to with a pissed off expression? He was obviously looking at me before hand, but the exasperated look wasn't AT me, he had the courtesy to look away before he made it.


Anyway that look was my sign to give it up with this guy, but then hate/blatant disinterest doesn't make sense when he's turned to face me and smile at me soon afterward. WTF is with that? I've never experienced it before. I've known complete avoidance/hate and it doesn't involve ever smiling at the person. He seems to be doing half and half. Could my desperation to look disinterested be making me appear totally unapproachable so he IS pissed off, but he's trying?