sexually active

i’m going on birth control for problems other than the birth control aspect of it. to help acne and hormones on my period. I’m not a virgin but i haven’t been sexually active in a month and i just got off my period. when they ask if i’m sexually active is it acceptable to say no? I’m 17 and my mom will be in the room and she doesn’t know that i lost my virginity so i’m not sure how to go about it...