Merina IUD

I got my iud about 3 weeks ago, and I just get my first period since and its lighter and not as crampy but I noticed last night on my pad, after having some intense cramps, that there were little clumps. I know this sounds gross but I just thought they were blood clots, they were so large though. I got worried and I picked one up to feel it with my fingers and it felt distinctly like a ball of flesh. It was weird and I'm super worried, idk what it is but I'd like an explanation to calm me down.