Birth control

I am 15 and I really want to go on the pill cause I’ve just had a pregnancy scare (I do use condoms) and I think going on the pill would be best but if my mum finds out I’m having sex she’ll be so disappointed and she doesn’t want to put me on it to help my period as she believes I should stay off it as long as possible so I don’t know how to bring it up in conversation to get her to allow me to go on it. I know if I’m having sex I should take the responsibility that comes with it but I could do with some help