Hi I was on depo after having my 2nd child I was on it for two and a half years. I was told it could take up to a year to completely come out of my system. When I came of it we were planing a pregnancy within the coming year. I had my period a couple of days after my injection was due, I didn't have another one, my daughter was born 10 months after I came off depo.
Everyone is different and are affected at different levels. So good luck I hope all goes well and you have a BFP very soon ;o)