Pregnant or not

Hi I’m on the implant I went on it February 2018 not long after I had my son in January I’ve been feeling quite sick today and had really bad heartburn and sore boobs my boobs are quite tender and have been for a few days now I don’t have any periods why I’m on the implant I don’t really want anymore baby’s just yet what can I do I’m scared if I’m pregnant... can I be or not as anybody fell pregnant on the implant? Thanks