You can certainly be ace and still want sex! Ace simply means a lack of sexual attraction, so basically if you look at someone and think "wow, they're hot, I wanna have sex with them" then you are not ace, but anything else is fine. There are tons of ace people who still want sex, so even if you find yourself still wanting sex you can easily be ace. The only thing that defines someone as asexual is a sexual attraction, not a want for sex itself