Hello, As you got two negative pregnancy test, then it is unlikely for you to be pregnant. Though you can undergo one blood test for beta hcg to exclude pregnancy completely. In exclusion of pregnancy, other reasons are ovarian cyst (most common), hormonal imbalance, stress/ anxiety, thyroid problem, wt gain/extreme loss, irregular eating habits etc. Do some investigations to rule out underlying pathology like USG lower abdomen, thyroid profile, blood sugar & other hormone assay etc. So consult with your gynecologist at the earliest and take suggestive measures. Avoid stress/ anxiety by regular deep breathing or yoga, take healthy diet with iron supplements, control body wt and maintain genital hygiene properly. If you need further consultation with me, then you can visit http://www.healthcaremagic.com/doctors/dr-soumen-patra/63326. Take care yourself.