What Could Abrupt Stopping Of Periods In 2 Days Mean?

i started my period on thursday. usually it lasts a full week...i had very heavy bleeding and threw 2 clots then after 2 days it stopped... nothing...just stopped... my husband and i has sex on the 4th day and i bled really heavy again all night and now thismorning nothing again! could i be pregnant or having a misscarrage? should i be very conserned?