I Have Been Off My Depo Shot For A Month

I have been off my depo shot for a month now. I have not started my period yet. Me and my husband has been having unprotected sex seen I stopped using the depo shot. I am trying to find out how long after I stopped trying the depo shot can I get pregnant. I am worried because I am a high risk pregnancy patient because of my blood type. I have took a home pregnancy test three weeks ago and it was negative was that to soon to tell