How many days should be considered haiz?

Since I became baaligh till I felt pregnant for my third baby, my haiz would last for a period of 6 days. After the birth of my third baby, nifaas and a period of 7 months ,my haiz started to become unstable. It would at times last for 7 days , 9 days over 10 days, etc. Each month different. After 3 years , I decided to see a doctor who diagnosed an outgrowth on one of my ovaries explaining this irregularity. Got the necessary medications and alhumdulillah It was removed. My haiz is slowly stabilising. I would like to know the number of days to be considered as haiz each month?