this shot causes all kinds of nasty things to our bodies....
Sometims birthcontrol can fail, but you should be proactive take a pregnancy test and make appt with a dr to have a Blood test to ensure your not pregnant.
In my limited experience with Depo, I know that it can sometimes fail even before your next shot is due. I also know that sometimes your fear of being pregnant causes you to have some symptoms of pregnancy. The best thing to to is to pee on a little stick and see what it says. If it's negative, your symptoms were probably psychosomatic and you'll return to feeling normal quickly. Good luck. :)