Is it normal to constantly have sex on mind

I know at my age it's totally normal to always think about sex, but i get so vulgar sometimes. and its constantly about weird scenarios like a husband & wife inviting me in bed with them. or my doctor taking my clothes off, or teachers keeping me after class. when people look at me, i guarantee that's like the last thing they think is on my mind, aha idk i think im driving my self nutts!!!!!