Birth control

Im 17 and i want to be put on birth control but i dont know how to tell my mom..
I get VERY bad cramps when im on my period and we scheduled a appt to go to the gyno for it but had to cancel it bc i was sick. My mom doesn't know ive had sex nor do i want her to know. Im not sexually active yet but im getting back with a guy & we probably will be sexually active within the next 5 months. I dont want my mom to think i want to get on bc bc im getting back with him & want to have sex with him.
Advice??