I had mine put in a couple months ago and I've had spotting almost the entire time and just got a period for the first time since post op bleeding stopped and I'm getting heaps of clotting like I did before I got the mirena (I got it for heavy and painful periods)
Reason I'm writing is the fleshy clots you speak of I had before I had mirena and my mother did when she was younger also - they can be just normal bodily way of expelling the used/unwanted lining from your body. Perhaps it's the hormone shift ? I'm still getting those fleshy clots as well as big red ones now I'm on mirena and today I was shaky with some weird tummy upset.