Had mirena. Unprotected sex. Light spotting, Stringy brown stuff from vagina. Suggestions?

I have had Mirena for three years ago. I've never had a period on Mirena. About 4-5 months ago I started getting light spotting, just when wiping. I had unprotected sex 8 days ago and just had log stringy brown Lucas like stuff come from vagina. I'm worried. It was coiled up like maybe I passed an unborn fetus, since I've heard of that previously happening. I have a picture of the substance. Once I uncoiled it. It just looks like mucasy tissue or something in shape of a worm. But it breaks apart. Also I was lightly spotting the day before sex. Please shed some light on the situation pleas.