Unprotected Sex Nexplanon

Sarah
Hello everyone, this may be personal but I have a question I recently got nexplanon. I got it on the third day of my period and today would make it a week of having it. I am in a monogamous relationship with my boyfriend of two years and I will see him tomorrow. My doctor said to use protection the first week but since tomorrow will be my 8th day and I am just wondering what is the soonest someone has had unprotected sex with the nexplanon (we plan on doing withdrawal, I know it's not 100% effective). As well as what is the soonest someone has seen side effects?