When exactly (on what day of your menstrual cycle) the bleedings occur might be very important. The menstrual cycle length you reported is rather shorter than expected. Therefore, it is possible that a hormonal imbalance might be present.
The two bleedings you experience in one menstrual cycle might be ovulation bleeding and your normal menstrual period. Ovulation bleeding is a bleeding that occurs when you have your ovulation. This bleeding occurs when the drop in hormones, which is a signal for releasing the egg, is rather fast and significant. The inner layer of the uterus recognizes this condition similar to the real period and starts small ovulation bleeding that is usually light and lasts for only a couple of days. Since the ovulation occurs exactly fourteen days before the start of the real menstrual period, you might want to calculate the days between the light bleeding and the bleeding that resembles a real menstrual period more.
You might want to visit your gynecologist to check for any hormonal imbalance. A physical examination and hormonal laboratory tests might be needed. If a hormonal imbalance is detected, you might be given certain medications (possibly containing hormones) to try to regulate the length of the menstrual cycle and the hormonal imbalance.