Being put on bc pls read I need advice!!!

Alright so I have extremely irregular periods and have been asking my mother to put me on birth control for a while. She is a major health freak and is convinced it's going to mess up my hormones I've even asked a doctor about it and he TOOK her side saying it effects natural Rythyms. I am now sexually active w/ my boyfriend ( my mother doesn't and cannot know this for a while) and in the midst a pregnancy scare. I know you can get brith control from planned parenthood but I would like to keep this as a last resort any ideas on how to get her to put me on any form of birth control?