Teacher problem

When I was in fourth grade and saw a really young girl heavily flirting my favorite teacher, I promised myself right there I'd never even think about anything like that. It was wierd, kind of creepy, and immoral, not to mention awkward.
Well, as of a few weeks ago I broke that promise. Im a senior in high school, and I really like my teacher. I hated admitting it, even to my best friend, but I really needed some advise. Some people laughed it off and thought I should enjoy it while it lasts, and some told me to forget about him. Im not looking for attention or think its cute. I was actually quite horrified when I realized this one sleepless night, but even that didnt make the feelings leave.
The teacher, he's great. We're six years apart, which makes it harder I think, since I've never really been attracted to older guys. I never thought this would happen to me. But he is acting really odd about this. Somtimes he's really fun to be around, and others he's deliberatly distant. And then the librarian told me he was in there the other day telling her how I was a great person and complimenting me. What is that?
It this normal? I think its illegal to have any sort of relationship with someone like him while I'm still a student in the school that he works at. This is his first year teaching, so its even more confusing. Does he know how I feel about him? Is it normal?