What Causes Delayed Periods With Spotting And White Discharge?

hello madam im 21years old.got married last year in the month of october.i hav a query on pregnancy.that is i hav missed my period in the month of january 8 this year n this is my 2 month continution but didnt get my period.during the third week i got spot which turned into black colour n now im getting white discharge.today i hav got the prega card n da answer was negative.kindly give me the possible answer.