If you spot once in a while while you are on depo-provera provera (medroxyprogesterone) does that mean your not pregnant?

No: You can spot for a number of reasons, including breakthrough bleeding (which is common among women on Depo-Provera provera). Spotting also can occur at time of implantation when you become pregnant. However, Depo Provera (medroxyprogesterone) is very effective at preventing pregnancy. The home pregnancy test is the most accurate method of determining if you are pregnant!