My periods are usually 27-29 days and last 5-7 days. I started on Tuesday and that made me 7 days early. Now today I started bleeding heavy, I went through 3 tampons in an hour. And I had passed a big blood clot. It was long and looked like a night crawler (spongy to the touch). After passing that my period is moderate and I have low back pain with mile-moderate cramping. I was wondering if I just went through a miscarriage. Oh, I have never passed a large clot before they usually came out in small sizes

That's a heavy bleed. I would go to the E.R. and be seen. Your health is important.

Did you find out whether it was a miscarriage? I'm going through a similar thing at the moment. Scary as all hell!