Ttc after depo

♡Alexa♡
So I had my son in September and went on depo at my 6 week appointment had that shot plus the second three months later I didn't get my third shot last month but I haven't started my period yet I'm almost a whole month sense anyone else have this problem how is can I get it corrected and how will it affect my ttc in a few months I'd like to start trying again when my son is 18 months