freshman

I'm currently a freshman in high school and i have feelings for a senior. he's 3.5 years older than me which i don't find weird at all, but i feel as if I'm being used by him. I'm a virgin, and he's not and i just feel like he's using me for sex, however idk if that is true. im bisexual and I've only dated females and so i don't know how to tell if a guy likes me or is just using me. is this wrong?