Spotting?? Period??

I missed taking my BC on Sunday. I usually take it at 830pm. On Monday I took 2 at 330 in the afternoon. Starting on Monday evening, I started having brown spotting and same with Tuesday. Today it was the same, but now there is a mixture of blood. Is this because of how I took my pills? I've skipped days before and have doubled up and this has never happened. My last period ended 9 days ago.