Is this pregnancy or just something normal?

IM SORT OF CONFUSED NOW I HAVE BEEN ON THE DE PO SHOT FOR ABOUT 2YRS NOW AND I WAS ABOUT A DAY OR TWO LATE GETTING MY SHOT AND DURING THE TIME ME N MY BOYFRIEND AT THE TIME DID HAVE SEX AND HE DID ADMITT TO RELEASING INSIDE OF ME NOW THAT WAS IN OCTOBER OF 2010 AND NOW I HAVE BEEN HAVING CRAMPS BUT NO PERIODS AND I USEALLY HAVE PERIODS ON THE SHOT. THE CRAMPS HURT SOOO BAD WHEN SOMETIMES I CANT SLEEP IN WHENEVER I RUN OR MOVE IN A CURTAIN WAY IT FEELS LIKE SOMETHING IS INSIDE OF ME BUT I CAN'T EXPLAIN IT WHAT CAN THIS BE? Could i be pregnant this whole time and not know it.