The quantity of blood discharged through the vagina is what mainly differentiates the two. With a menstrual period, there is a heavy flow of blood that can last for an average of three to five days. Ovulation, on the other hand usually brings spotting or a little bit of blood. This blood is either dark brownish red color or pink and there is very little of it. It may be mixed with cervical mucus and may be accompanied by mild pain in the stomach or some cramping that resembles menstrual cramping.