I am 38 years old, three years back i took regesterone before 5 days of start of menstrual cycle and postponed to 7 days after 3 days periods started with severe stomach ache, fever, chillness, sweating and i was unable tosleep on my back, heavy bleeding with lumps. From then 4 years i am suffering with same problem little bit reduced as of now to 2 days of begining. I consulted doctors they did scanning to find any fibroid present but found nothing and now i take pain killers continuosly three time s from 1st day to third day of the period contains Aceclofenac and Dotropine i think . I think this as side effect of Regesterone .