How do I read this Scorpio man? (Scorpio answers appreciated)?

I'm a pisces girl and I've known this scorpio guy for 2 years in college. This year I've really started to like him. As far back as I can remember, I would catch him in cl staring at me across a distance and looking like a hypnotized little boy. I smiled back at him, but didn't convey any romantic interest because I already had a boyfriend. This year, I find him staring at me again, mostly with the "little boy" stare and one time I caught him looking at me seductively and chewing pionately on his pen. I did a cl presentation one day, and he approached me after and told me how good it was. I realized that I liked him and I wanted to hang out with him to try to "test out the waters" and to gauge how he feels about me. I arranged to have a study session with him to write a paper (start off slow), but he seemed nervous the whole time and ended up leaving early. I ran into him the next week and he was really talkative and enthusiastic, and he asked me to turn his paper in for him because he wouldn't be in cl that day. Now he seems more publicly aloof from me than he was before I actually hung out with him, but he still keeps staring at me from across the room like always. I don't understand how to read him ... I still like him, but I almost feel like he's afraid of me now or something. Am I wrong in uming he likes me? If he does like me, will he come around eventually and stop being so hot and cold? How should I let him know I care without going overboard?