Teens on birth control?

I'm 17 years old and I have been with my boyfriend for almost 2 years now. I am thinking about going to planned parenthood, and getting on birth control. My mom refuses to get me on birth control as it makes her worry that It would be "encouraging us to have sex". I have tried many different things, like saying my periods are heavy, or I want it just in case, or that my cramps are bad. She doesn't want to hear it.  Now, I want to be safe, so I decided to go and get on it myself. I want to know what method would be the best option for me, health wise, secrecy wise, and preventing pregnancy. All help would be greatly appreciated. Thank you guys!!