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Most likely the spotting is due to the emergency contraception (EC). They commonly will reset your period and lead to irregular bleeding. I do recommend you take a pregnancy test. A pregnancy which occurred from intercourse 14 days ago or earlier will be accurate at detecting pregnancy. Follow the instructions carefully using your first urine of the day after not drinking overnight. If it is negative, most likely your symptoms are because your body is trying to normalize itself after the EC. If you had intercourse less than 14 days ago, repeat the test weekly until you have gone 2 weeks without unprotected intercourse or you start your period or have a positive result. As an aside, periodic use of condoms does not effectively prevent pregnancy. I would recommend you consider using a daily form of contraception to prevent you from having to worry when something like this happens. If your pregnancy test is negative, you can expect your period to resume in 6 weeks after taking the EC.
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