Hello, In general, home pregnancy test or blood test for beta-HCG gives accurate result after 7 days of missed period. Early pregnancy test may give false negative result. So, you can repeat those tests. In exclusion of pregnancy, other reasons are ovarian cyst , hormonal imbalance, stress/anxiety, thyroid problem, weight gain/ extreme loss, irregular eating habits, psychological factor etc. Need to investigate properly to pin point the diagnosis by USG lower abdomen, complete hormone assay, thyroid profile, blood sugar & prolactin level. Consult with your gynecologist for proper guidance. You may need to take hormonal medication with other supportive therapy. Avoid stress/ tension, take healthy diet with Vitamin & iron supplements, control body wt by regular physical exercise and take sound sleep.