Telling my mom I'm sexually active...

I need help, I'm 16 and me and my boyfriend have been together for 17 months and we just started having sex this past week. how do I tell my mom I'm sexually active? I want to get on BC and like I need to go to the doctor about it but I don't know how to tell her and how she will react. The thing I'm most scared about is what if I tell her and she doesn't let my boyfriend come over or spend the night as much or at all, what if she's mad that I am sexually active? Also can I make my own appt without my parents knowing?