Is it normal that i keep having sexual thoughts for a teacher?

Alright so, this bullshit started in freshman year (which was last year). And one of my friends told me about her algebra teacher who asked out a fellow female freshman, and how she rejected him and cried because she was freaked out. I had a different teacher at the time so I had no idea how he looked like, until she described him to me I was like, "Wait, I know this guy!" So, the guy is plus sized, he's got a pretty nice beard, a comb-over, he looks like he's in his late 20s, early or mid 30s. Who knows. Turns out he's married, no kids. Ever since that day i've been learning new things about him and see him in the halls, but of course, I keep it down. I honestly don't know what the fuck has gotten into me but, I honestly think it's the fucking beard. He just looks so awesome in that beard. Fun fact: he's been flirting with other students as well. He told some girl, "If I wasn't married, i'd be with you." Which I thought was hilarious. I've also been having weird thoughts and sexual fantasies about him, mostly about him taking me from behind on a desk, choking me, pulling my hair, spanking me, calling me a bitch, etc. (Which is strange since i've never been into rough sex to begin with but recently i've been into it, i'm also a virgin.) But yeah, just wondering, is this shit normal? (Also, I'm aware that it's illegal, and that i'm basically putting his job at risk, but don't worry about it, i'm too fucking shy to make a move anyways.)