I want to go on the pill

I want to go on the pill becuase I don’t fully trust using only a condom. I haven’t had sex before but me and my boyfriend really want to im just paranoid that I’ll get pregnant. I don’t know how to tell my mum that I want to go on it because I’m not 18 yet so I can’t get a prescription from the doctor without my Mum finding out so I really don’t know how to tell my mum without her freaking out. I’m over the legal age so she can’t stop me but I still just don’t know how to tell her. Any advice please xx