Shedding uterine lining with mirena?

I got mirena put in about 2 months ago, no complaints. I've been spotting since but it usually gets slightly heavier around the time my period is supposed to come, but the spotting is no biggie to me or my boyfriend. My question is, I *think* I had my period a week ago (I'm not even completely sure when I get it at this point due to the consistent bleeding lmao) but today I've been sort of cramping and when I went to pee **tmi** this dark flesh looking thing about an inch long came out of me, but no blood. I was thinking it was maybe my uterine lining but I thought that would come with blood, you know? I'm not even sure. I don't really know what to expect from my body with this iud.