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The breast tenderness could be due to water retention as part of a complex called Pre-menstrual tension. The brown discharge could be due to bacterial infection in the vagina. It can be Bacterial vaginosis
or possible STDs which can only be confirmed by testing. Avoid sexual intercourse without use of condom for now till you are diagnosed and treated. Better to also get a Pregnancy
Test to confirm pregnancy or not as well. Consult your Gynaecologist as soon as possible for early diagnosis and treatment and prevention of complications.