Missed Period / Negative Test Results

My period is very regular (27 day cycles), My period was due Oct. 10th and has yet to come down today Oct. 13th. I have taken 2 pregnancy tests, however, they have come back negative. My nipples are very sensitive and tingly. I also have some slight cramping as if though I was about to get my period. Is is to early to test? We have been having unprotected sex and we did have sex during my fertile period.