If you had read the information that comes with the depo medication, you would have seen that the symptoms of this medication include weight gain and also consistent bleeding for a number of months. I don't understand why people don't research the medications they're about to be on.
Depo is the safest and the most effective birth control method out there - it's 99.9% effective, unlike the pill which can be as low as 80% or even lower, depending on how you are will your birth control pill taking. Being off on taking your pill even by 30 minutes can affect you and make it easier for you to get pregnant.
That being said, I have been on the depo shot for over two years now and yes you bleed for the first couple of months. It says that in the side effects section of the medication information. But after that you stop having your period because you stop ovulating. If you don't ovulate why would your body build up the blood and tissue in your uterus? That's why the period stops.
I gotta tell you, I haven't missed having my period on bit. It's heaven. No more cramps, no bloating, no nothing. It's fantastic.