What Causes Dark And White Discharge In Periods?

i had regular periods till last month. i should hav got it buy 25th of last month but it didn t come . i waited for 12 days. but didnt get it. so i took some pills which is used to get periods. my periods started two days ago. it was slightly dark till yesterday night. but today morning it was very thich and and somthing slightly whity(like te white which comes out of our face pimple). its smelled bad and i felt like i was abot to faint. im worried about this whity substence.