What is this??? Dont look at pic if it may be disturbing

C

Hello everyone,

Of anyone can please share some light to what this is or have experienced something like this. On my 4th day of period where its heavy this came out. At first I thought it was a miscarriage but now I'm thinking it can be an Endometrial cast. I have had miscarriages before but this may be what it is. Please if anyone can shed some light and sorry for the pics! Please dont look at them if blood and stuff like that grosses you out