IM 15 YEARS OLD AND NEED UR HELP

HI WELL IM 15 AND MY LAST PERIOD WAS DEC 24 2006 AND IT STOPPED ON THE 30TH IM USULLY LIKE 28-30 DAYS APART TILL MY NEXT PER AND ITS THE JAN.29TH AND I HAVENT GOTTEN MY PER YET ON THE 21I STARTED GETTING SOME BACKAKES AND SOME CRAMPS ON MY SIDE LIKE IF MY PERIOD WOULD COME BUT IT DIDNT I FEEL BLOATED TIRED AND IVE BIEN FEELING NAUSEAS ESPECIALLY IF I GO IN A CAR I GET STOMACH SICK AND NAUSEA I TOOKA PERGNANCY TEST ON THE 24 IT WAS NEGATIVE AND ITS JAN 30 AND I HAVENT GOTTEN MY PERIOD COULD I BE PREGNANT????HELP :$