i had unprotected sex on july 5th, i took plan B the next day. i got my period on july 15 and i think it looked normal because i filled my pads and it lasted a week. then i got my period on august 18th which also lasted a week.i havent gotten my period this month but i think its normal because ive always had an irregular period. Ive taken three HPT and all came negative. could i be pregnant?