being turned on

hi, im 18 years old and nothing really turns me on. like my boyfriend says that certain things i do is really hot and turns him on. however i dont get the same things with hik or anyone else for that matter. i dont really feel that urge. i guess i used to when i was younger maybe. dont get me wrong sex feels pretty good. but i never ever get turned on- as in wanting to has sex really badly. And i never look at guys (or girl's) and feel attracted to them. ive also never had an orgasm during sex. any ideas why this is?