Skyla to mirena? How did it change your flow?

I have the skyla. I've had it for almost 6 months now. My periods are irregular now and it's annoying. The doctor that I talked to about getting an iud i had never seen her before. She wound up moving or getting fired so I got it put in by someone else. I had no idea that Skyla isn't as likely to stop your periods or make them lighter/spot like mirena until after. Has anybody made the switch between the two? How did it effect your flow?