I had sex for the first time in November and have had my regular periods up till January where i completely missed it. then i got it the beginning of February. In December i went to the GYN and got a pregnancy test that was negative i also had a sonogram done and the doctor assured me i wasn't pregnant but now i have back pain and a fluttering in my lower abdominal... could i still be pregnant or i'm i just freaking myself out????