What Does White Tissue Discharge During Periods Indicate?

Hi, I miscarried about 5 months ago and have had 3 periods since. I seem to be ovulating properly and my periods have come each month within a couple of days of the last months period. I thought I might be pregnant this month, but I got my period. However today I passed a solid piece of white tissue during my period and had unusually painful cramps last night for 5 minutes. Is it possible I miscarried?