i can help: first of all, if you can't write fantasy, and if it keeps on turning into something else, then just don't write fantasy. it probably just isn't your style. But if you really, really want to write fantasy, i recommend you go to the library, and get a bunch of fantasy books, as well as some other genres. read them, and compare them. and take notes. lots of notes. note's on what makes fantasy fantasy, and what makes si-fi si-fi. then, when you're writing, constantly be checking your note's, making sure that you're writing fantasy, and not something else.