I've been on the depo shot for a year now. No break through bleeding the whole year until recently that last almost a week along with nausea through out the whole day/night moodiness increase hunger and tired more than usual. Can I be pregnant?

Its possible... no form of birth control is 100% effective...

Pregnancy is possible any time you have sex. No form of birth control is 100%. There are many people on this site alone that got pregnant while on the Depo shot.

In other words, yes, you could be pregnant.