NOT SURE IF I AM OR NOT PREGNANT

Im having the same problem. I was supposed to get my period between the 23rd-28th this month (Dec). The first day of my last period was November 23rd. My days to concive where 12/05/08 to 12/07/08...My boyfriend and me had sex on the 21/06/08..I took 3 pregnancy test the first one came out positive and the next two came out negitive!!