Hi,
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Your symptoms (tender breasts, missed periods, frequent urination, mood changes, abdominal cramps, changed bowel habits) could be suggestive of pregnancy. You should consider visiting your doctor/gynecologist for examination (to confirm pregnancy related changes/signs in body) and a blood/serum HCG level test (to confirm/rule out pregnancy accurately). Urine pregnancy tests usually start being positive after about 1 week of missing periods. Sometimes urine tests can show false negative results too, because urine pregnancy test kits are calibrated ones, so they show positive results only after the hormonal levels in urine have reached a certain level.
Take care.