hi, i had sex on October 28th, one day after my period had ended. i have a 7 day period and a 30 day cycle. i was expecting my period on November 21st but it came on November 15th. its wasn't like it usually is. it was very clotty though it was pure blood and it didn't stop for full days.. only for a couple of hours. it did last for 7 days. so on November 22nd i took a pregnancy test and it came out negative. i had been feeling a bit nauseous and my breasts seem larger but no soreness at all. today (Nov 26) i went to the drug store and got another pregnancy test and it was negative again... could it be my period that started early because of painful sex or is it something else?