miscarriage?

I had spotting mid cycle which isn't normal for me and cramped pretty bad a week before my period was due. Mine only ever lasts 5 days and it's day 4 and still heavy and I'm still cramping pretty bad. I had a blood clot about 3 inches long yesterday. Is this just a bad period or could it be a miscarriage? Husband and I are TTC but I try not to test until I'm 3 days late.