Just tell her you want to be safe, it doesn't necessarily mean that you are being sexually active, birth controls can also help with periods and cramps. I told my mom a long time ago I wanted to be on birth control, but she threw a fit when I brought it up, at 18, I was on the pill but it caused a bunch of negative effects and I didn't have the money to get an IUD, so I just stayed faithful to condoms. At age 20, I ended up getting pregnant (even though I was married) but I am seeing now babies are a TON of work. I wouldn't hide it from your mom, I would just be open and honest with her about it. If she gets mad, just let her get over it because in the long run, YOU want the birth control to protect yourself from pregnancy, and I am sure that she will thank you some day for taking the responsibility and wanting to be on it.
If you are having sex, you should always protect yourself from STD. Always use a condom, if you ain't already. If you don't tell your mother, or afraid to have that talk, there are always free women clinics you can go to. But advice, do tell your mom. Because if something comes up that's way to handle by yourself, your mom will be even madder that you didn't tell her in the first place.
My mom just knew the first time I had sex. Yes she was mad, but at the end of the day she came around, and we got to the clinic, and was put on the pill. :)
Well I'm 17 and I'm going to turn 18 in 3 months. So I thought that since I'm going to be 18 soon that I should start on the pill
I would just tell her you want to be protected. I guess it all depends on things like your reason for wanting to be on birth controle and your age some birth comtrol can effect puberty as well.