Non stop bleeding with first period after implant

So I just got my first Nexplanon implant. And the Dr told me I may not get my next period, or it would be very light. I did end up starting to bleed a few weeks after getting the implant. It started out as light spotting for a couple weeks everyday all day. Now in the third week of this bleeding cycle the bleeding has gotten super heavy and the cramping has intensified immensely. My question is: Is it normal to bleed non-stop like this for weeks after the first implant, or should I be concerned that something may be wrong? I researched other areas online and it seems to say that if I don’t stop bleeding after 6 MONTHS to talk to my doctor, but that can’t be right. Has anyone else experienced this? Is it normal or should I see my doctor?