Why Does One Have Heavy Periods & Spotting?

my ex boyfriend and i had sex less then 3 weeks ago, and i usually get my period around the end of the month begining of next, well i had gotten it early and the first day was very heavy then the second it had just stoped and i threw up that day several times too. Then the next two days i felt sick but still no period and had not throw up again then i wake up and im spottin then it stops, then wake up again and im spotting. what does this all mean?? am i pregnant?