Symptoms of pregnancy - On Depo?

There is a possibility of becoming pregnant on the Depo shot. It is 99% effective, which means that 1 or less women out of 100 become pregnant while using this form of birth control. When I was on the depo shot I had a lot of undesirable side effects that mimicked pregnancy, such as weight gain, mood swings, extreme hunger, and food cravings. But since you have been on the shot for a year and a half and have not had these side effects before, it seems possible that you may be pregnant. I would take a home test and see the results, and call your gynecologist for possible reasons for the sudden change.