getting pregnant on the implant ? help

I think I'm just worried but I had my first implant in for 3 years and didn't get pregnant once and my periods stopped. and my second implant has been in about 3 months and haven't been pregnant  and my periods have stopped too.. However isit possible to still get pregnant on it depending on the person? My last guy told me how one of his ex mr's got pregnant on implant by him and now his most recent one is pregnant from him aswell( we arnt together no more) he seems to have good sperm and I have felt abit sick in the morning recently .. We slept together abour 2 weeks ago, I think im just worrying and being silly but obviously could my implant work one day and the next not ??