Longer Menstrual after 3rd child..

I had my last and final baby Back in November.. Its now June, 6 Months of my menstrual being waaaay longer than usual.. Currently on day 8 and its still going.. I don't get why.. I had my tubes tied? Could that have effected it any? I was regular 6 days.. I could've planned it out to a T on when I would Start and Finish.. Now... Who knows.. It can last up to 12 days.. 8 days of on and 4 days of after spotting.. Help!!! It's driving me crazy!!