Pregnant or just worried?

Ari • Have been with my SO since we were 14. We`re both turning 21 this year. ❤️
I have been on birth control for almost three full months now, taking it at the same time every night and never missing a day. My boyfriend and I had sex two weeks ago without using a condom for the first time, but withdrew before he finished. 
I'm supposed to start my period today but I haven't yet. I wasn't worried but now I'm starting to. Maybe it is just late but I'm not sure.