everyone is convinced I'm pregnant but...

Hi,
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Although irregular periods are associated with anovulatory menstrual cycles, it is possible that you have occasional ovulation. If you had been sexually active around ovulation time, then your symptoms of increased appetite, headache, frequent urination, increased tiredness, absent periods, mood changes, abdominal distension could suggest chances of pregnancy. The urine pregnancy tests done very early in pregnancy can show you false negative results as the kits are calibrated ones, so unless the hormone levels in urine reach a certain level, they do not show positive results. The test should always be done on early morning first urine sample to get accurate results (pregnancy hormone HCG is believed to be in highest concentration in this sample, and you should avoid lot of fluid intake and caffeinated beverages in the night before taking the test). If you have persistent symptoms suggesting pregnancy, or if you suspect to be pregnancy, visit your doctor/gynecologist for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet.
Take care.