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The time of your unprotected intercourse is around the probable fertile period (time of egg release from ovary as suggested by the changed vaginal discharge). The symptoms (headaches, constipation, appearance of Montgomery tubercles around areola, feeling sick) could be suggestive of early pregnancy. If you suspect to be pregnant, visit 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. If you want to go ahead with the test, consider waiting for your periods, and test with the early morning first urine sample (avoid having lot of fluids in the previous night).
Take care.