Depo has gotten a pretty bad rap, I know a lot of women who have been really messed up by it. A moderator here, by the name (and screenname) of Kristine actually went on LC to improve symptoms caused by Depo, among other things. You may want to check out her story.

In general, chemical contraceptives can stall weight loss in some people. The only way to know for sure is switch brands, I think. Are you experiencing other unwanted side effects?

Hope you figure it out.