ok i missed a few pills and had unprotective sex with my fiance of 2 years..

wednesday was the first day of a missed period...i took a test it was positive i had a feeling i was pregnant as my boobs have been tender and i have felt sick and dizzy i am now having back aches almost like my period is on its way ...i have had no bleeding whats so ever..

today is saturday and this morning i took another test which was negative but still no bleeding. whats happening?? am i pregnant?? :-(