Could I Be Pregnant When I’m On Birth Control And Took Plan B After A Condom Broke?

I’m on birth control but a condom broke on august 27 so I also took a plan B the same day and continued the birth control and now the veins in my boobs are more noticed should I be worried about pregnancy. I took a pregnancy test today (9/12) and it was negative but is it to early to be negative for real?