Hello, First of all, you should undergo one blood test for beta-HCG and ultrasound scan at the earliest to exclude pregnancy. It also helps to rule out underlying pelvic pathology. Other reasons are hormonal imbalance, irregular diet habit, stress/ anxiety, ovarian cyst, thyroid disturbance, increase prolactin level etc. Here, you consult with your gynecologist after getting initial test reports to proceed other relevant investigation & next line of management. Try to avoid mental stress, take healthy diet with Vitamin & iron supplements, maintain genital hygiene and take adequate bed rest. Be well and take care.