Hey, im 16 years old and i had sex with my boyfriend a few weeks ago and we used protection. i was supposed to start my period the week after but i didnt. it has been about 3/4 weeks now and it still hasnt come! i was also gettin sore breasts especialy round th nipples which are swollen, headaches dizzyness Constipation and nauzia. i took 2 tests about a week ago but they both came out negative. if im not pregnant whats wrong with me?!ADVICE PLEASE?