AF?!?!?!

Ive always had moderately heavy periods. Even while on the pill it didn't seem to change my cycle or flow as I have always had a 29 day cycle. This is my first month off bcp in three years and thus my first "real" period in three years. AF came on cd32 which is different but what I don't get is that I'm bleeding SO bad and my tummy is sore. I know that can be signs of endo, but I really don't think that would be it as I have never had this issue before. I don't get it. Any advice?