Why is he always doing this?

my lecturer acts quite strangely around me, he usually looks in at me whenever he walks past the room i'm in, and yesterday after he'd been talking to me and my friend, i had joked around with him about something, almost teasing him, and after that he went to tidy up a draw or something, and just looked over at me and stared o_O then a little while later i was in my room at the beginning of lunch, washing my hands at the sink, and i had been talking to my friend that was in the same room, and when i looked round the other way i caught my lecturer just standing and looking at me from about halfway down the corridor and i felt freaked out cuz i wondered how long he'd been standing there, just watching me wash my hands lol, and as soon as i looked round at him he immediately looked away and started walking away down the corridor, as though he had suddenly remembered something that he needed to do :/ and when he comes into my room to talk to other people, he will walk past my desk and hover, just watching me or watching what i'm doing, as if he's going to say something but often doesn't. i find it a bit freaky lol, why do you think he does all this? :/