Is there a chance of me getting pregnant?

Nikki
So I got the nexplonan implant in about two days ago and was on oral birth control for two months up until I got the implant in. My doctor said that it would be effective immediately since I was already on birth control up until then. She also said because of that I could have unprotected sex and be okay. Does that sound correct or is there a chance I could end up pregnant again. I'm almost three months postpartum.