Birth control is highly effective at preventing pregnancy. Obviously, it is WAY too early to determine if pregnancy occurred, despite using birth control. In the future, you may want to ask your boyfriend to use a condom for additional protection against pregnancy. Condoms also protect against most STDs, unlike birth control.
What birth control are you on? It's surprising since you are on "birth control", you are very concerned that having sex will lead to pregnancy, is why I ask.