Mirena coil and unusual heavy period

[Tiggerish]

I have had a mirena for over a year now and have had regular but very light periods since. Out of the blue I had a heavy one - like I used to get before it was fitted.

Has anyone else had similar? Does it mean it has shifted about and isn't working properly?

(It's definately still there btw)

I had the Mirena put in back in March and no bleeding since, until August, when I had a 14 day period. It was lighter than usual, but lasted a fortnight. Dr sent me for a scan and I was told I had a cyst on my left ovary, which apparently aren't uncommon with the mirena and the bleeding I had could be from that. Dr didn't seem overly concerened or recommend any treatment. and I've had nothing since.
hth

Also ... (TMI) ... I passed two lumps of tissue-type stuff (not normal period blood clots), and the nurse who scanned me mentioned that could be the cyst breaking up and dispering.