TMI what is this?

Nearly 6m postpartum. I have the Paraguard IUD. I feel like it’s not in correctly as the length of the string changed drastically and I have had sharp pains while inserting a tampon since I noticed the length of the string. Last night I was having INSANE cramps and all of a sudden this popped out of me. I continued to bleed/cramp pretty profusely through the night and still am.

It was very firm. Much firmer and much larger than any of the chunks I’ve ever had. Some clearer/gray tissue in the middle surrounded by the deep red.