After two weeks i had unprotected sex, lately i been getting pregnancy symptoms; like nausea , bloating , craving, headaches , lower back pain , and stomach pains. Two weeks ago i think i had my period, but it was very very light and was on and off for a weeks. And plus I m also on birth control.Today i took a pregnancy test and it was a negative,now I have stomach pains now again, please tell me what i do??