I am 21 and had unprotected sex on 12/27/12 (fertile day) then again on 12/28/12 (ovulation day)....my period came a little early on 1/11/13 was a lot lighter than usual and only lasted 4 days....my usual period is super heavy lasting almost 7 days....i took 2 HPTs both came out negative....should I get a blood test done or wait and take another HPT?