What do you do when you've gotten too close to your teacher?

My teacher is a nice guy, probably in his late 20s. I keep on seeing him everywhere, and I admit, I do think about him a lot ... (I think I'm falling for him!) I had to email him for homework and we ended up having a nice little conversation, but I think it might have gotten too personal because he suddenly just said, "Let me know when you're done with your paper" and ended the conversation. I know for a fact that the stuff he told me wasn't anything he hadn't said to the whole class at one point or another ... but now he's just being distant and purely professional in his responses. I tried to make it seem like I was totally unaware that we had crossed some kind of boundary or something, but I think he knows that I have feelings for him! What should I do now?