How do I talk to a strict mum about an implant?

Bethanie
Hi so I'm 16 and have been with my boyfriend for two years. My mum knows I'm on the pill because of my messed up heavy periods, but she doesn't know that I also use them for contraception. Im of age to have legal sex and also to make my own decisions about my health. I could have an implant without her permission, but if I have one and she finds out I'll be in more trouble than if I tell her beforehand. But how do I go about doing that? It will help me get through college pregnancy scare free (we use condoms too) and it will soothe my awful periods without me having to remember to take a pill every day, because I'm very forgetful. Any advice will be welcomed, thanks c: