Periods while on depo

Am I the only one who gets NO period while using depo? My first round of depo shots I got one very light then it went away and the other months I would have "ghost periods" so I would get all the symptoms of my period but not blood. I missed a few shots so I had to start again, I assumed the process with my period would be the same. But this time I have no period whatsoever. Or could I be pregnant? Uh-oh........