Decidual Cast or Period??

So I’ve been “spotting” for over a week, I thought it was just from possibly rough intercourse or breakthrough bleeding as I am on the NuvaRing and use that continuously to skip my period but once that “spotting” lasted over a week I took my ring out because I was getting nervous and a bunch of blood clot-like things came out in the shower, the bigger looking one was not clot-like and had almost a tongue-like consistency, almost solid honestly. (Pictured.TMI). I’m having pretty intense stomach cramping that comes and goes in waves since around that same time as the passing of those unknown clots in the shower and I’m still having clot-like things show up in my underwear and urine. I’ve also taken two pregnancy tests which were definitely negative on both. Is this a decidual cast or a weird side effect of my ring? Please help & does anyone know if I have to go into my doctor to get these tested for anything to know if it’s a decidual cast or not? 😅