Depo Vera

I have been on Depo for almost a month now....the same day i got my period is when i got the first shot...i have had my period ever since although for the most part it has been very light...and than just this week it started to get heavy and now it light again....is this normal??? Also i have headaches all day...feel nauseas, and have cramps...is this normal?? Even though im prevented from getting pregnant...is it still possible to get pregnant while still taking the shot?? My boyfriend thinks he can ejaculate in side me now that im on the shot and i was wondering if this happens too much will I end up pregnant??? How will i know i am??