Bad bleeding with Nexplanon

I got the Nexplanon implant put in in April of this year (8 months ago) and everything was fine at first and my periods were normal. My periods were regular up until recently- I have been on my period almost this entire month (3 weeks) and it is showing no signs of stopping. I have experienced horrible cramps throughout the entire 3 weeks and they got even worse the last few days. I am not sure if this is normal and if anyone else has experienced this or if I should go to the gyno?