Is it normal that i think about fucking a specific sexy girl all day?

it goes like this, there's a beautiful girl who I really feel attracted to, and it's been quite a while, the thing is, I specially think of her being fucked by me... but what I'd REALLY like to do is fuck her ass, like literally fuck her in the ass, I'm guessing that's a laughing matter I reckon that but, problem is, that's too much of a big deal to ask someone I know, cause my friends could think I'm crazy. If you want to know a lil bit more, I also would dig her as my GF and all that. I don't know what to do, I feel like a perv thinking about her like that.