birth control

so i’m a junior in high school and i’ve been messing with this boy since my freshman year and we want to have sex. i just don’t know how to tell my mom i want to get on birth control. my mom and i are super close and she’s really chill but idk how to bring it up without making it awkward which ik is unavoidable. i also have really painful periods which i could use as an excuse but idk what to do