TMI!!!

I begin having light pink and brown spotting and stinging near my right ovary 2 days before eventually the flood gates opened "literally". So my "period" came 4 days early and this would be day 3. After dealing with excruciating cramps and bleeding extremely heavy for the past few days...this fell out of me while showering tonight. What is this? Uterine lining or possible miscarriage? My cycle usually starts off heavy but not like this one. I've had small pieces of tissue on all of my tampons since its started.