What Causes Light Periods Along With Burning Sensation?

Hi, iam 26 years ,165cm and my weight50.ihave no problem befor ,ihave reguler cycle came every 27 days for 5 days with average amount,no abnormal vaginal discharge but last 3 mounth ihad burning menstrotion and low blood flow with dark color for 2 days then menstrution stop. iam not on any chronic medication ,or alchohle intake. e