Well, if you have been getting your depo shots on time then you are probably not preg. But like all BC there is a small chance of pregnancy
You probably just have the flu, but if you want to be sure then take a preg test and see. If you've stopped your period, or still feel unsure about the first results-- being that it was only a week ago, you should test after a missed period-- then wait 2 weeks or so and take another home preg test just in case. Couldn't hurt right? Good luck