Pregnacy and Depo-provera

The last time I got a depo shot was in December 2011. I didnt recieve my next shot April 2011 instead i started da birthcontrol pills and my dr warned me that it could make me fertle snce the depo levels are low and i should use backup(condoms,spermicide,etc)I stayed on the pills for two weeks and then i stoppd taking them. I Started my period a few weeks later exactly on time. it last for a full 6 days and was normal.the next month when it was sapposed to come on it only spotted for a few days (i have had unprotected sex during the time between periods) is it possible that im pregnant considering that i was on da depo in december???