Had protected sex 1x since period 1wk ago. now cramping, dark brown discharge, thick mucous, very little blood on and off. is this a cyst or ovulation?

Hard to know: A normal menstrual cycle (from the first day of one period to the next period) lasts 21 to 35 days. It is normal to bleed for up to seven days. Bleeding in excess of seven days or bleeding in between the two periods is considered abnormal. It could be a cyst, a polyp, a fibroid, or even an infection. Better see a doctor to get checked.