Convincing mom

Cynthia
Soo I'm 19 and sexually active and want to get an IUD. I told my mom I want one "to regulate my period" but she said they probably won't let me unless I'm sexually active. I keep bugging her about it but she keeps saying the same thing. I've considered telling her I'm sexually active but... She's kinda nuts. I don't mean normal motherly instinct nuts. She's literally nuts and would probably go psycho on me. I love her to death I'm just not sure how to tell her without her getting pissed and going psycho on me. I would just get one without telling her but she has my insurance card and all that other stuff plus I'd need someone to take me to the appointment. Advice on how I should go about this?