Hello dear Understand your concern I manage this type of case with following possibility. 1. Pregnancy: pregnancy may be cause if you had unprotected sexual intercourse in fertile period of cycle. As slight bleeding in you case is may be due to implantation bleeding. That is just like spotting or mild bleeding. Wait for week more to bleed. If it will not come and then I advice you to go for home pregnancy test to confirm the pregnancy. Blood HCG and USG should be done for accurate confirmation of pregnancy. 2. Missed abortion: As you passed brown blood clots, it is sign of missed abortion. Should be diagnosed by USG scan and if retain product will found should be treated by misoprostol or by D & C. Pregnancy tests was negative as you did very early. 3. Ectopic pregnancy should be rule out by USG scan as it also cause brown blood clots pass but it generally associated with abdominal pain. 4. Ovarian cyst/PCOS: it can also cause delayed period due hormonal imbalance and bleeding due to rupture of cyst. Should be diagnosed by reproductive hormone analysis and USG scan. So consult the near gynecologist for proper treatment if period will not come. Hope this may help you Best regards Dr. Sagar