Irregular bleeding

I am now 41 years old and for the pass 3 or 4 years I have been getting haidh for more than 10days. It first starts off with a brown discharge and after a a day or two I start to bleed for 7 days and thereafter I have the brown discharge again for the next few days. This whole discharge and bleeding goes on for more than 10 to 12 days. Do I start counting my days from the day of discharge or the day I start bleeding and must I go back to following what my past habit was 7 to 8 days a few years ago or do I have a ghusul after 10 days?