I want to go on birth control but my mom says no.?

So i'm 18 and i want to get on birth control because I am not a virgin anymore so it makes sense to me to get on it. So I asked my mom if I can get on it to regulate my period (she doesn't know i lost my virginity), but she said no and that i should wait because when I get on it it will be harder for me to have children in the future. I think she is waiting until i'm in a serious relationship, but I don't want to wait. How should I convince her without seeming to suspicious about the whole losing the virginity thing? btw people i dont regret it and i dont need the whole you're too young bs. thanks!!