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Urine pregnancy test results rarely show false positive results. If the test has come positive it is likely that you are pregnant as suggested by your symptoms (abdominal cramps, low back pain, tiredness). Look out for development of any other new symptoms. Wait and watch for your next periods. If you do not start with periods within 10 days of expected period dates or if you develop any new symptoms suggestive of early pregnancy, or if you get abnormal periods, visit your doctor/gynecologist for further examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). Take adequate rest. Drink plenty of water. Maintain healthy diet.
Take care.