Late period-birth control failure or symptom?

I got my first depo shot a little over a week ago I was due to start my period at the beginning of the week and no symptoms yet. AmyonAnyone who has had the depo-did your period stop and if so how quickly did it stop? I only worry because my bf had unprotected sex first night of my ovulation. They took a test before I got my shot and it was negative but I'm afraid it may have been too soon. Just a little concerned..