If the bleeding gets extremely heavy, i would contact your healthcare provider. The hormones in the rod may be interacting with your body a bit differently now, but I cannot give you a definite answer.
With me, its the opposite. I was told my periods would go away after a few months. Nope. Still getting them 7 months later.
Bottom line is, everyone's body is different, and reacts differently.
I am here if you need to talk. Hope this helped.