pregnant on nexplonal? need feedback

so I've been on nexplanon implant for 3 years I've tried to get it removed 3 times and they couldn't find it in my arm told me it was in my muscle and I would need surgery so I decided to way it out because it was supposed to run out after 3 years being December 2017. now my sister also has the nexplanon and when she went in to get hers switched out for a new one they then told her the one she had was good for 4 years now is that true is my birth control still in effect ? I've been having unpertected sex for 3 months can I be pregnant or is my birth control still in effect? help me plz