Birth control for 16 year old

I have been wanting to start birth control for a long time now. My periods are very painful and I just have a lot of problems when I'm on my period. Also I've been thinking about becoming sexually active. The problem is my mom is completely against me getting any kind of birthcontrol. She feels as though I shouldn't be doing anything in the first place so I don't need it. I've looked online and seen lots of options but my thing is I don't know how I can I get birthcontrol without using my insurance but not have to pay an arm and leg.