It's not about fidelity or divorce, I hope it's ok to post this here. I'm still a student & having a happy relationship with someone else (my boyfriend). We've known each other for 2 years by now. Thing is one of my instructors at school has been acting strangely towards me. I had 1 class with him last semester: a biology class. There was practically nothing back then, I was just one of his many students. He's very popular in the department and among students since he's still not married, knowledgeable & quite handsome! I like his teaching style so I re-register for his class again this semester, we only meet once a week. I'm terribly quiet among others even in class, maybe that's why he notices me since the last semester. When we meet again in the same setting, I myself notice his attitude is quite strange.

When I sit at one place, he often passes by and acts as if it's on routine. He never touches me or anything like that, but I still feel it. Whenever I look up and saw him, he looks at me in a more intimate way. And there are sometime when we were in the alley leading to classroom with many others, he'd find a way to walk close at me. These days I've had some personal family issues to worry about and kinda low on energy & somehow show it in class, he acts as if he's on the same track and let class leave too early. 

Again, there's basically nothing between us now, but I'm worried when thinking about that. I like him but more like a friend since he's still young. Don't want to hurt his feeling and I'm not 100% sure about his behavior by now. What should I do to improve this? just have no chance to talk directly to him that I'm having somebody else. I've tried to keep a distance with him and don't look at him directly much, but I have 3 more months ahead. To think I have to act like that for several more months make me feel uncomfortable in a way. Any advice or sharing would be much appreciated.