Late period or miscarriage?

AF was 5 days late. No signs she was coming or anything. Checked my cervix last night and it was high and my mucus was clear. Woke up this morning in extreme pain and heavy bleeding. In less then 12 hours I've gone through 3 almost 4 pads (I normally use 1 MAYBE in that time frame). I just went pee and noticed very large chunks of stuff (TMI sorry). Is this just an unusual period or could it be a miscarriage?