tired of being scared every month

Kellyzully • enjoy :-)
I've been with my boyfriend for over 2 years and we've been sexually active this entire time. he uses a condom. But every month I worry about when my period will come, if it will, some months I've even gotten so stressed I cry and cry! it always comes but I'm so tired of that end of the month stress! The thing is, I know there's other forms of contraception, but I'm 17 so I need consent from a parent.
My mom doesn't know I'm sexually active, I'm sure she assumes but I've never had the "where do babies come from" talk with her. I don't know if I should talk to her and ask to visit a doctor for Birth Control but there's a 50/50 chance she'll won't be okay with all this ): what can I do?