Period hasn't come??

La

My period was suppose to start yesterday but it still hasn't come I've been having brown spotting for 3 days now and that's it. I have been on BC for almost 3 months now, I'm a bit concerned. Is it worth taking a pregnancy test? I had my son 3 1/2 months ago, could this just be the BC? I haven't missed one pill, I take it the exact same time every day.