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If you are not on any regular birth control measures, and had been sexually active without protection, chances of pregnancy are possible. The symptoms that you describe could be few of early symptoms suggestive of pregnancy. Wait and watch for your next 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 get 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). 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). If pregnancy gets ruled out, further evaluation would be done to look for the underlying cause for your symptoms and missed periods. Treatment as appropriate (based on examination findings and investigations results) would be started to help you control the symptoms and get your periods. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Take adequate rest. Drink plenty of water. Maintain healthy diet and lifestyle.
Take care.