Advice please

My mom is super protective. She had me out of wedlock so I've been taught growing up not to have sex until I'm married. However Im in a long term relationship and I am sexually active however my mom does not know. I've done a really good job at hiding it from her but now I want to get an IUD and I'm still on her insurance. Should I tell her that I'm thinking about getting one? She might kill me and I know she's going to make things awkward. She might even be weird about me and my boyfriend being alone again if she knew