I Am 3 Weeks Pregnant And Have Had Brown Discharge

I am 3 weeks pregnant and have had brown discharge for the last 4 days. I don't have any cramps or anything with it. It's starting to worry me. My period is due at this time too and I was wondering if that had anything to do with it? My boyfriend and I also had sex a night or two before the spotting begun. Is this normal or does it mean miscarriage?