Is this a miscarriage? TMI

My husband and I have been trying for a baby, last month i had a few days where I spotted in and off and I didn’t really think much of it because I have PCOS. I was also taking ovulation tests and they always had two parity dark lines when usually the test line is barely noticeable on mine. I didn’t really know what was happening but I just went on with it. Friday August 3, I was at work and started having this God awful back and stomach pain.. I would be checking in a vendor and I would have to stop and grab my back because it was terrible. I went to the bathroom and I had bled through my pants, it was a good amount of blood. I wiped and this HUGE, thick thing came out. I posted it below. I’ve never had anything like this. My periods are never heavy. Well the bleeding lasted maybe 2 Days and now all I have coming out is white discharge. I’m still cramping and my back is still hurting and my nipples are still very sensitive. Is this a miscarriage? I can’t get in to my dr until Thursday. Thanks so much for the help.