Can't Stop Thinking About Him

I'm a first-year law student and I have this thing for my TA. We're both adults and there's nothing wrong in that sense. But it feels like cheating even though we haven't done anything yet. Every time he walks by, all I can think about is how his shirt fits so well, and those eyes... It's getting harder to focus on class. Should I tell him or just let this be my secret? What do you guys think?