late period but I have symptoms of it

i got married on july 19th 2008 and for the next three nights we had sex but on the third day during sex i started bleeding. i had to leave that day and go out of toen for three weeks but the dried bleeding continued for 3 days...now its august and my period should have come on the 6th but it has not come i took two first response pregnancy test and they were negative what should i do......i feel sypmtoms like i have a period but it has not come...