depo shot

Okay so I've been on the depo shot for a month now and I started having a super light period exactly a week ago and some days it was non-exist. But when I'd have sex there would be a little bit of pink in my discharge. Well normally my periods don't last a whole week but this one pretty much has. I was told I wasn't suppose to get my period on this and I'm super frustrated. I really hope today is the last day of this. It will be 8 days tomorrow... ugh.