Nexplanon implant?

I got the implant at the beginning of my last period as instructed by my gynecologist on the 2nd day of bleeding. Afterwards I have had no side effects or irregular bleeding. I did wait out the two weeks with protected sex (condoms) as recommended by the doctor.

Now as my period should be starting I'm roughly 4 days late. I heard the implant can stop you cycle all together. I have some minor cramping and a headache...some pms like symptoms but nothing that is indicating that my regular period is about to begin.

Is this normal? Should I be worried?