How to ask for the pill...

So I’m 17 and sexually active, but without my parents knowledge. I obviously have sex with condoms, but I think I want to add the pill or the bar into the mix just as an extra safety insurance.

Unfortunately I’m not too sure how to bring this up with my parents, as I’m not actually in a relationship... I’m just having sex with my best friend. I don’t necessarily want to tell them I’ve been having sex... so how can I ask for a form of birth control without giving it away, because when I asked at the age of 16, mum thought it was weird and said I didn’t need it.... 😬🤷🏼‍♀️