experiencing extreme fatigue, irritability and tender breast

Hi,
Welcome to ehealthforum,
Although PCOS is associated with irregular periods and anovulatory cycles (menstrual cycles without periodic egg release from ovary), there is possibility of having occasional ovulation, and if you had been sexually active around ovulation time, and if semen or pre-cum has come in contact with vagina, chances of pregnancy are possible. The symptoms that you describe (extreme fatigue, irritability, tender breasts) could be few of early symptoms suggestive of pregnancy. You can get false negative results with urine pregnancy tests done very early in pregnancy, 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). Wait and watch for your periods. Look out for development of any other new symptoms if pregnancy is suspected. If periods do not start within 10 days of expected period dates, or if you have got abnormal periods, or if you suspect chances of pregnancy, consider visiting your doctor/gynecologist at the earliest 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 and lifestyle.
Take care.