How do I go about this? HELP!

I want to start going on the pill but I dont know how to go about it with my mom because she doesn't like the idea of me having sex because when she found out I was having sex she pretty much didnt talk to me or look at me for days. She also told me it was wrong what we did and even took the condom out of the trash kept it and told my boyfriend if he did anything she would sue him because he is turning 18 while I am still 17. My boyfriend and I still do it though but we just want to take extra precaution and have me go on it. During an argument me and her had about her taking it out of the trash and how she "didnt raise me to be this way" she told me if I wanted to go on it to tell her but I feel as if she really didn't mean it. How do I ask her or even bring it up if this topic is so sensitive to her?