Well, it's hard to say with such limited details. Did you have unprotected sex and at what part of your cycle did you have it? The two weeks of brown/black bleeding are odd. That's too long for a normal period and more like spotting old blood. I'm confused by some of the other things you say. When was your last normal period? Personally, if you've had sex . . . I'd take a home pregnancy test to rule out pregnancy. And if you aren't pregnant, monitor your next period and if it is still this same pattern of old blood/spotting rather than a period, see your doctor to evaluate your hormones. Let us know what the home pregnancy test says. good luck