I Have Been On The Birth Control Combined Pill For

I have been on the birth control combined pill for over a year now and I have never had break through bleeding and I always get my withdrawal period on the Tuesday or Wednesday of the placebo week. On Friday when I was still on my active pills I had dark brown bleeding which I thought was just old blood but then it turned darker red color and required tampons for two days then it stopped on Sunday. On Sunday night is when I took my first placebo pill and now every day since that I have had just very light brown spotting in the mornings but then it stops. Could this be because the breakthrough bleeding happend so close to my placebo pills, or did my period just come early? I'm worried am confused to why this is happening. I took one pill about 4 hours late on Wednesday so I don't know if that has anything to do with the breakthrough bleeding.