Pregnant.....? Please help......

Had my first baby October 21 and I bled for about two weeks stopped and then started bleeding again Like November the 18th. I assumed that it was my period. Bled all the way until the end of the month. Got on DEPO on the 5th of December. She said wait 1-2 weeks to have unprotected sex. So me and my fiance used condoms for like a week and a couple of days and then stopped. Didn't have my period last month around the 18th but my stomach has been cramping lately and kinda nauseous maybe.. Ive been on depo before for a couple years on and off and its always been have a period for like 2-3 weeks then not have one for like 2 months on depo. Could i be pregnant....