Am I pregnant I had sex on the 1st of oct., and started my period on oct. 10, 2011. It normally stays on for a week but this month only stayed on four days. On the 19th I began spotting accompanied with light cramping the next day. The bleeding continued

Yes. Yes it is still possible that you are pregnant or worse have what is known as an ectopic pregnanyc where the prenancy is growing outside of the uterus where it should be. This is very dangerous. You should see a physician either at an urgent care or emergency room to recheck your pregnancy test and perform an exam immediately.