I just finished my period 2 weeks ago, and I'm usually very regular. I've been on birth control for 4 years with no problems. However, I had a situation where I had a small amount of dark brown or black discharge. It was just a tiny bit, and only happened once. I haven't had any abdominal pain or other problems. Is it just left over from menstruation or should I see a doctor? I visited my gyno about 2 months ago and she said everything was fine. No stds, and as far as I know I'm cervical cancer free. What is it?