TMI PIC Grayish tissue/cm mixed with period blood.

Was cramping since last night. Woke up and had a little blood clot. Then it stopped for about an hour . then it came full force and 2 pad changes later I go to the bathroom and there's this. I've never had this much "extra" discharge before. I started today and my period was 10 days late. Took a test at 7 days late and was negative. What could this be.