Mom Won’t Let Me Go On BC!

I’m 16. I’ve been w my bf for 7 months and we r definitely ready to have sex. My mom met my bf for the first time a couple of months ago and she thought him and I just met. Everything has been going well and I thought I’d ask my mom abt BC just in case I decide to have sex I’ll be prepared and ready. I pulled out every card trying to convince her. I told her my periods been weird lately and BC would fix that etc. She got a little mad and said “there no need for u to be on BC at this age” like omg would u rather have a grand kid? What do I do? Advice please.