period changes after Pregnancy??

so I am on my second period since I gave birth in Feb and have noticed they are now excruciating and alot heavier then before and I mean alot. my first one I figure it was normal since just having a baby But this one is so heavy and the pain was so bad last night I nearly threw up from the cramping and I have a high pain tolerance. anyone else experience this or possibly know what could be going on? just curious because my period has never been anything like this even with all the cramping.