I Am A 29bf And I Have Endo N Poly

I am a 29bf and I have endo n poly syndrome. I also have thyroid issues. However my period has been almost perfect for about six months like clock work. This period is different I started on the 22 and I had horrible pain n very heavy bleeding. I would change my tampon twice maybe three times n a hour. Then the pain got so bad a tampon gave me more pressure so I went to pads. Now its day two and I'm barley bleeding its more of Brown like then end of a period. What's the reason for this thank you for your time
Mrs.Kincer