Discharge

Hannah
So I'm on the pill and have been for 2 and a half years. I usually 'skip' 2 periods then have one. This time I accidentally skipped 3 and I have a week left on this lot of pills before I get my period. Today I had some cramps and when I went to the bathroom there was some brown discharge in my panties. I take the pill at roughly the same time everyday- within the hour of normal time when I can't take it right on time and have never missed a pill. Does anyone know what this is?