Birth control question!!!

After my son was born 8 months ago I had the implant put in to my arm when he was 6 weeks old, his dad and I split up a few weeks before I got the implant, i still have normal periods and now I am engaged to my best friend but he also has a 9 month old baby so we agreed on no babies for awhile! We've been having unprotected sex and now my period is late and I have been feeling so nauseas all the time, has anyone else been pregnant while on the implant?