Irregular menstrual bleeding. Of it.

On December 5 I got a period. It was light on 1st day and from 2-4 day it was medium level bleeding. I normally used to get heavy bleeding when I get periods after month lasting for 4 days with cramps as I have irregular menstrual cycle. Then on 5 day there was a spotting and disappeared. But again on 7 day I got a little bleeding which was light only. From 8 day for 2-3 days I got spotting and again it stopped. Then again spotting started. I got Spotting once or twice a day. But since last 5-6 days I'm again getting medium level bleeding. I experienced a bearable cramp for 2 days. Also I'm going to see gynaecologist tomorrow. But just now I just saw a chunk of blood clot when I emptied my bladder. it was larger than normal clot. even though I'll be seeing gynaecologist tomorrow still I'm scared. what might be the cause of it. I'm worried whether it's because of something serious.