I'm on birth control (Alesse 28) and have been for almost a year. My boyfriend and I rarely have unprotected sex and if we do he never ejaculates inside of me. Anyways the other day (Friday) I noticed what looked to be a brown spot in my underwear. We had had sex this day but it had been protected. The day after noticing the brown spot I had mild cramping but I still have about 7 pills in my pack to go so it's not a period or anything.

I have not missed a pill either but I have been taking them at varying times of the day (I usually take it at 7pm but sometimes because of work I've been taking it at like 9pm)

Could this be causing me to spot? Or is this like a weird side effect of birth control I've never had. I don't want it to be pregnancy but I know that not everyone has implantation bleeding so what gives?