There is usually more cramping w/ the copper IUD compared to the Mirena. More cramping, heavier periods, and more intense cycles are not uncommon w/ the copper.

I started w/ the copper IUD and kept it for about 18 months. the cramping was HORRIBLE. Really heavy periods that did not subside. I had it removed, and didn't do any BC for awhile b/c we decided on baby #3.

After baby 3 was born, I went with the Mirena. Awesome. No cramping, no periods, no nothing. I don't even notice it's there. I've had it for 2 years now.

Anyway, back to the OP, definitely have it checked. It's not uncommon for the side effects to get worse over time, so the cycling may be just coincidental. You might have gotten the side effects w/o the cycling. Hopefully it didn't shift out of place.